We made a very minor change to the apex class where we included a field in the Email mathod in the class, however when we tried to deploy we get attempt to de-reference null object error.
Test class:
 

public static testMethod void testUpdateRegistration2(){

Course__c newCourse = new Course__c();
newCourse.Total_Sessions__c = 3;
newCourse.Session_No__c = 001;
newCourse.Registration_Time__c = '8:45AM';
newCourse.Number_of_Days__c = 1;
newCourse.Name = 'Apex Test Course';
newCourse.Minimum_Attendee__c = 5;
newCourse.Maximum_Attendee__c = 10;
newCourse.GST__c = 10;
newCourse.GST_Exempt_Course__c = false;
newCourse.Course_Type__c = 'Face to Face';
newCourse.Course_Start_Time__c = '9:00AM';
newCourse.Course_Number__c = 'C001';
newCourse.Course_End_Time__c = '5:00PM';
newCourse.Course_Classification__c = 'Public';
newCourse.ChargeID__c = 'PRC_999';
newCourse.Category__c = 'Food';
newCourse.Base_Price__c = 999;
insert newCourse;

datetime t = System.now();
date today = Date.newInstance(t.year(),t.month(),t.day());

Class__c newClass = new Class__c();
newClass.Name = 'Apex Test Class';
newClass.Minimim_Attendee__c = 9;
newClass.Maximum_Attendee__c = 99;
newClass.Course_Name__c = newCourse.Id;
newClass.Class_Location__c = 'Sydney';
newClass.Class_Begin_Date__c = today;
newClass.Class_End_Date__c = today;
newClass.Number_of_Confirmed_Attendees__c = 10;
newClass.Class_Status__c = 'Open';
insert newClass;

Account newAccount = new Account();
newAccount.Same_As_Address__c = 'true';
newAccount.Name = 'Apex Test';
//newAccount.ParentId = newAccountParent.Id;
newAccount.Mailing_Zip_Postal_Code__c = '2009'; 
newAccount.Mailing_Street__c = 'Fake Mailing Street';
newAccount.Mailing_State_Province__c = 'NSW';
newAccount.Mailing_Country__c = 'AUSTRALIA';
newAccount.Mailing_City__c = 'Sydney';
newAccount.CurrencyIsoCode = 'AUD';
newAccount.Business_Zip_Postal_Code__c = '1000'; 
newAccount.Business_Street__c = 'Fake Business Street';
newAccount.Business_State_Province__c = 'NSW';
newAccount.Business_Country__c = 'AUSTRALIA';
newAccount.Business_City__c = 'Sydney';
newAccount.Account_Classification__c = 'Business';
insert newAccount;

Account newVenueAccount = new Account();
newVenueAccount.Same_As_Address__c = 'true';
newVenueAccount.Name = 'Apex Venue Test';
newVenueAccount.Mailing_Zip_Postal_Code__c = '2009'; 
newVenueAccount.Mailing_Street__c = 'Fake Mailing Street';
newVenueAccount.Mailing_State_Province__c = 'NSW';
newVenueAccount.Mailing_Country__c = 'AUSTRALIA';
newVenueAccount.Mailing_City__c = 'Sydney';
newVenueAccount.CurrencyIsoCode = 'AUD';
newVenueAccount.Business_Zip_Postal_Code__c = '1000'; 
newVenueAccount.Business_Street__c = 'Fake Business Street';
newVenueAccount.Business_State_Province__c = 'NSW';
newVenueAccount.Business_Country__c = 'AUSTRALIA';
newVenueAccount.Business_City__c = 'Sydney';
newVenueAccount.Account_Classification__c = 'Business';
newVenueAccount.Type = 'Venue';
insert newVenueAccount;

Contact newContact = new Contact();
newContact.FirstName='John';
newContact.LastName='Doe';
newContact.Phone='0299998888';
newContact.Email = 'john.doe@fake.com';
newContact.AccountId = newAccount.Id;
newContact.Dietary_Requirements__c = 'ABC';
insert newContact;

Contact newContact1 = new Contact();
newContact1.LastName='Master';
newContact1.Email = 'a.master@fake.com';
newContact1.Phone = '0288889999';
newContact1.AccountId = newVenueAccount.Id;
insert newContact1;

Contact newContact2 = new Contact();
newContact2.Job_Title__c = 'National Manager';
newContact2.LastName='Master';
//newContact2.Email = 'a.master@fake.com';
newContact2.AccountId = newAccount.Id;
newContact2.MobilePhone = '0499999999';
insert newContact2;

Trainer_Approved_Course__c tac = new Trainer_Approved_Course__c();
tac.Name = 'Apex Trainer Approved Course';
tac.Trainer__c = newContact.Id;
tac.Expiration_Date__c = today + 100000;
tac.Course__c = newCourse.Id;
tac.Approved__c = true;
tac.CurrencyIsoCode = 'AUD';
insert tac;

Trainer_Approved_Course__c tac2 = new Trainer_Approved_Course__c();
tac2.Name = 'Apex Trainer Approved Course 2';
tac2.Trainer__c = newContact2.Id;
tac2.Expiration_Date__c = today + 100000;
tac2.Course__c = newCourse.Id;
tac2.Approved__c = true;
tac2.CurrencyIsoCode = 'AUD';
insert tac2;


Class__c newClass1 = new Class__c();
newClass1.Name = 'Apex Test Class';
newClass1.Minimim_Attendee__c = 9;
newClass1.Maximum_Attendee__c = 99;
newClass1.Course_Name__c = newCourse.Id;
newClass1.Class_Location__c = 'Sydney';
newClass1.Class_Begin_Date__c = today;
newClass1.Class_End_Date__c = today;
newClass1.Number_of_Confirmed_Attendees__c = 10;
newClass1.Class_Status__c = 'Open';
newClass1.Trainer_1__c = newContact.Id;
newClass1.Trainer_2__c = newContact1.Id;
newClass1.Venue__c = newVenueAccount.Id;
newClass1.Num_Material_Ordered__c = 10;
newClass1.Date_Material_Ordered__c = today;
newClass1.Num_in_Stock__c = 10;
newClass1.Num_Material_Printed__c = 5;
newClass1.Num_Standards_Out__c = 10;
newClass1.Num_Standards_In__c = 10;
newClass1.Boxes__c = 2;
newClass1.Job_Reference__c = 'N/A';
newClass1.Date_Material_Sent__c = today;
newClass1.Comments_Materials__c = 'N/A';
insert newClass1;

Id[] originalRegIds = new Id[0];
Registration__c newAttendee = new Registration__c();
newAttendee.Course_Name__c = newCourse.Id;
newAttendee.Attendee__c = newContact.Id;
newAttendee.Class_Name__c = newClass.Id;
newAttendee.Total_Amount__c = 999;
newAttendee.Status__c = 'Confirmed';
insert newAttendee;
originalRegIds.add(newAttendee.Id);

Registration__c newAttendee1 = new Registration__c();
newAttendee1.Course_Name__c = newCourse.Id;
newAttendee1.Attendee__c = newContact.Id;
insert newAttendee1;
originalRegIds.add(newAttendee1.Id);

Registration__c newAttendee2 = new Registration__c();
newAttendee2.Course_Name__c = newCourse.Id;
newAttendee2.Class_Name__c = newClass.Id;
newAttendee2.Attendee__c = newContact.Id;
newAttendee2.Status__c = 'Pended-SAI Cancellation';
insert newAttendee2;
originalRegIds.add(newAttendee2.Id);

Registration__c newAttendee3 = new Registration__c();
newAttendee3.Course_Name__c = newCourse.Id;
newAttendee3.Class_Name__c = newClass1.Id;
newAttendee3.Attendee__c = newContact1.Id;
newAttendee3.Status__c = 'Confirmed';
insert newAttendee3;

Registration__c newAttendee4 = new Registration__c();
newAttendee4.Course_Name__c = newCourse.Id;
newAttendee4.Class_Name__c = newClass1.Id;
newAttendee4.Attendee__c = newContact2.Id;
newAttendee4.Status__c = 'Confirmed';
insert newAttendee4;

Certificate_Template__c newCertificateTemplate = new Certificate_Template__c();
newCertificateTemplate.Name = 'Apex Test Certificate Template';
newCertificateTemplate.CurrencyIsoCode = 'AUD';
insert newCertificateTemplate;

Certificate_Type__c newCertificateType = new Certificate_Type__c();
newCertificateType.Name = 'Statement of Attendance';
newCertificateType.Course_Name__c = newCourse.Id;
newCertificateType.Certificate_Title__c = 'Statement of Attendance';
newCertificateType.Certificate_Template__c = newCertificateTemplate.Id;
newCertificateType.Certificate_Options__c = 'Always Issued';
insert newCertificateType;

// reset governor limit
Test.startTest();

Assessment__c newAssessment = new Assessment__c();
newAssessment.Name = 'Statement of Attendance';
newAssessment.Assessment_Title__c = newCertificateType.Id;
newAssessment.Assessment_Status__c = 'Competent';
newAssessment.Attendee_ID__c = newAttendee.Id;
newAssessment.Assessor__c = newContact.Id;
newAssessment.Received_from_Assessor__c = today;
insert newAssessment;

Assessment_Competency__c newAssessmentCompetency = new Assessment_Competency__c();
newAssessmentCompetency.Name = 'Apex Test Assessment Competency';
newAssessmentCompetency.CurrencyIsoCode = 'AUD';
newAssessmentCompetency.Competency_Code__c = 'ApexTest_9999';
newAssessmentCompetency.Assessment__c = newAssessment.Id;
insert newAssessmentCompetency;

Invoice_ENT__c newInvoiceENT = new Invoice_ENT__c();
newInvoiceENT.Registration__c = newAttendee.Id;
newInvoiceENT.CurrencyIsoCode = 'AUD';
newInvoiceENT.Base_Price__c = 998;
newInvoiceENT.Payment_Status__c = 'c';
newInvoiceENT.Invoice_Type__c = 'ACR';
newInvoiceENT.Bill_Type__c = 'EAR';
insert newInvoiceENT;

Invoice_ENT__c newInvoiceENT1 = new Invoice_ENT__c();
newInvoiceENT1.Registration__c = newAttendee.Id;
newInvoiceENT1.CurrencyIsoCode = 'AUD';
newInvoiceENT1.Base_Price__c = 998;
newInvoiceENT1.Payment_Status__c = 'c';
newInvoiceENT1.Invoice_Type__c = 'REG';
newInvoiceENT1.Bill_Type__c = 'PUB';
insert newInvoiceENT1;

 try{
    Integer processType = 1;
    ClassObj.classcancellation(newClass.Id, processType);
    ClassObj.sendAttendanceList(newClass1.Id);
    ClassObj.sendAttendanceList_TIS(newClass1.Id);
    //System.assertEquals(0, classObj.checkPendingRegos(newClass.Id));
} catch (System.EmailException e){
    System.debug('we caught a email exception: ' + e.getDmlMessage(0));
}

Test.stopTest();

From the above code bold syntax is the line number 1071

Please find the image below of the error I get during deployment.

Class:
 

WebService static Id[] sendAttendanceList_TIS(Id ClassId) {

//Modified by sneh@sqwarepeg.com to include more venue and class material details
Class__c classObj = [Select Trainer_1__c, Trainer_1__r.Id, Trainer_1__r.Email,Trainer_1__r.EmailBouncedDate, 
Trainer_1__r.EmailBouncedReason,Trainer2__c, Trainer2__r.Id, Trainer2__r.Email, Trainer2__r.EmailBouncedDate, 
Trainer2__r.EmailBouncedReason, Trainer_2__c, Trainer_2__r.Id, Trainer_2__r.EmailBouncedDate, 
Trainer_2__r.EmailBouncedReason,Trainer_2__r.Email, Id, Venue__r.Id, Venue__r.Name, Venue__r.Business_Street__c, 
Venue__r.Business_City__c, Venue__r.Business_State_Province__c, Venue__r.Business_Zip_Postal_Code__c, 
Venue__r.Business_Country__c, Venue__r.Website, Venue__r.Phone, Venue__r.Internet_Email__c, Venue__r.Comments__c, 
Course_Name__r.Name, Class_Location__c, Class_End_Date__c, Class_Begin_Date__c, Num_in_Stock__c, 
Num_Standards_Out__c, Num_Standards_In__c, Num_Material_Printed__c, Num_Material_Ordered__c, Job_Reference__c, 
Date_Material_Sent__c, Date_Material_Ordered__c, Comments_Materials__c, Boxes__c 
From Class__c where Id =:ClassId];

//Modified by suzan@sqwarepeg.com, validation of the bounced emails
//Modified by sneh@sqwarepeg.com on 12/02/2009 to incorporate the Primary_Venue_Contact__c functionality
Contact[] conObj = [Select Id, Email, AccountId,EmailBouncedDate,EmailBouncedReason From Contact where AccountId =:classObj.Venue__r.Id and Primary_Venue_Contact__c = true];

//Contact[] conObj = [Select Id, Email, AccountId From Contact where AccountId =:classObj.Venue__r.Id];
//Query course field to add them in the Email template.
Course__c crs = [select id,Current_Revision__c from Course__c limit 1];
//if (classObj.Trainer_1__r.Email != null || classObj.Trainer_2__r.Email != null || conObj.Email != null) {
String jobTitle;
String email;
String phone;
String mobile;
String dietaryNeeds;
String accessNeeds;
String HTMLBody;

List<Id> RegIds = new List<Id>();
RegIds = getConfirmedIds(ClassId);

HTMLBody = 'Hi,<br><br>';
HTMLBody = HTMLBody + 'Please find attached the Attendance List for SAI Global\'s course.<br><br>';
HTMLBody = HTMLBody + 'Please print off a copy and hand to the Trainer on the morning of the course.<br><br>';
HTMLBody = HTMLBody + 'If you have any questions please don\'t hesitate to contact our Customer Service Team on 1-800-374-3818.<br><br>';
HTMLBody = HTMLBody + 'Kind Regards,<br>Training and Improvement Solutions<br><br>';
HTMLBody = HTMLBody + '<b><u>Course Information</u></b><br><br>';
if(classObj.Class_End_Date__c != null){
    HTMLBody = HTMLBody + 'Course Name: ' + classObj.Course_Name__r.Name + '<br>' + 'Current Revision:' + crs.Current_Revision__c.format() + '<br>' + 'Class Dates: ' + classObj.Class_Begin_Date__c.day() + '/' + classObj.Class_Begin_Date__c.month() + '/' + classObj.Class_Begin_Date__c.year() + ' - ' + classObj.Class_End_Date__c.day() + '/' + classObj.Class_End_Date__c.month() + '/' + classObj.Class_End_Date__c.year() + '<br>';
} else {
    HTMLBody = HTMLBody + 'Course Name: ' + classObj.Course_Name__r.Name + '<br>' + 'Current Revision:' + crs.Current_Revision__c.format() + '<br>' + 'Class Dates: ' + classObj.Class_Begin_Date__c.day() + '/' + classObj.Class_Begin_Date__c.month() + '/' + classObj.Class_Begin_Date__c.year() + ' - N/A<br>';
}
HTMLBody = HTMLBody + 'Class Location: ' + classObj.Class_Location__c + '<br><br>';

From the above code, The bold Syntax is line 429.

Please advise.

Thanks