Hi.......am working with webservices.  In That i have to check one field ...if it is null or blank also it should insert that record...

The filed name is  Workplace_Id and in sfdc it is picklist datatype....see the code below ...and when i insert the record with space ...i am getting error like 'malformed Id'....

global class InboundLinxUserRegistration
   {
     global class dtRegistrationInput
     {
       webservice String UserId;
       webservice String First_Name;
       webservice String Last_Name;
       webservice String Email_Address;
       webservice Id Workplace_Id;
       webservice String Workplace_Name;
       webservice String Workplace_Province;
       webservice String Workplace_City;
       webservice String Workplace_Postal_Code;
       webservice String Workplace_Address;
       webservice String Speciality;
     }
     global class dtRegistrationOutput
     {
       webservice date mydate;
       webservice String added;
       webservice String status;
       webservice String Message_Text;
       webservice String error;
     }
     public webservice static dtRegistrationOutput userregistration(dtRegistrationInput userregistration)
     {
       dtRegistrationOutput retvalue=new dtRegistrationOutput();
       List<Account> account = [select National_Code__c,PersonEmail from Account where National_Code__c=:userregistration.UserId OR PersonEmail=:userregistration.Email_Address];
       RecordType rec=[Select Id from RecordType where Name='NVS Profesional WEB'];
       Id RT=rec.Id;
       If(account.size()>0)
       {
           retvalue.mydate=system.today();
           retvalue.added='false';
           retvalue.Message_Text='Duplicate';
       }else{
               Account acc=new Account();
               If((userregistration.Workplace_Id!=NULL)||(userregistration.Workplace_Id!=''))
              {
                acc.Primary_Parent_vod__c=userregistration.Workplace_Id;
               }
               String Med='MED-';
               acc.National_Code__c=Med+userregistration.UserId;
               acc.FirstName=userregistration.First_Name;
               acc.LastName=userregistration.Last_Name;
               acc.PersonEmail=userregistration.Email_Address;
               acc.Account_Status_NES__c='Pending Approval';            
               acc.Primary_Address_2_NES__c=userregistration.Workplace_Name;
               acc.Primary_Province_NES__c=userregistration.Workplace_Province;
               acc.Primary_City_NES__c=userregistration.Workplace_City;
               acc.Primary_Postal_Code_NES__c=userregistration.Workplace_Postal_Code;
               acc.Primary_Address_1_NES__c=userregistration.Workplace_Address;
               acc.Specialty_1_vod__c=userregistration.Speciality;
               acc.RecordTypeId=RT;
               try{
                    insert acc;
                    retvalue.added='True';
                    retvalue.Message_Text='Registration Successfull';
                  } catch (Exception e){
                          retvalue.mydate=system.today();
                          retvalue.added='false';
                          retvalue.Message_Text=e.getMessage();
                    }
            }
            
       return retvalue;
     }
   }