While I am trying to Save data in Server side below error is captured:
An internal server error has occurred
Error ID: 694637652-163917 (119852647)
On checking logs there is null pointer exception and I can see regForm instance is holding "NULL" value.
Below is the component and controller code:
Component Code

<aura:component controller="admtest__.SaveRegistrationFormDetails" implements="force:appHostable,flexipage:availableForAllPageTypes,flexipage:availableForRecordHome,force:hasRecordId,forceCommunity:availableForAllPageTypes,force:lightningQuickAction"
                access="global" >
    
    <aura:attribute name="abc" type="String"/>
    <aura:attribute name="Name" type="String" default="" />
    <aura:attribute name="ParentName" type="String" default="" />
    <aura:attribute name="StandardOrClass" type="String" default="" />
    <aura:attribute name="NumberOfStudyHours" type="String[]"
                    default=" , Less than an hour ,In between 1 to 4,
                             In between 4 to 8, More than 8  hours" />
    <aura:attribute name="UsersResponse1" type="String" default=""/>
    <aura:attribute name="MobileNumber" type="Integer" default="" />
    <aura:attribute name="RegisteredCourseBefore" type="Boolean" default="false" />
    <aura:attribute name="InterestedInOnlineCourse" type="Boolean" />
    <aura:attribute name="CheckBoxvalue" type="Boolean" default="false"/>
    <aura:attribute name="PageHeading" type="String" default="Registration form for Students"/>
    <aura:attribute name="EducationalDetailList" type="List" default="[]"/>
    <aura:attribute name="RegForm" type="admtest__Registration_Form__c" default="{'sobjectType' : 'admtest__Registration_Form__c'}" />
    <br/><br/>
    
    <div class="slds-page-header">
        <div class="slds-align_absolute-center" style="height: 5rem;">
            <div class="slds-text-heading--large">
                <div class="slds-m-*_large">
        {!v.PageHeading}
                </div>
           </div>
    </div>
    </div>
    
    <div class="slds-size--5-of-8">
    <lightning:input label="Enter your Name" name="StudentName" value="{!v.RegForm.Name}"/>
    <br/>
    <lightning:input label="Enter you Parents name" name="parent" value="{!v.RegForm.admtest__Parent_Name__c}"/>
    <br/>
        <lightning:input label="Enter your Class " name="StandardOrClass" value="{!v.RegForm.admtest__Which_Class__c}"/>
    <br/>
    
    <lightning:select name="numofStudyHrs" label="How many  hours do you Study"
                      value="{!v.RegForm.admtest__Study_Hours__c}">
            <aura:iteration items="{!v.NumberOfStudyHours}" var="hrs">
                <option value="{!hrs}" text="{!hrs}"/>
        </aura:iteration>
    </lightning:select>
    <br/>
    
    <lightning:input name="MobileNumber" label="Phone Number" type="telephone" value="{!v.RegForm.admtest__Mobile_Number__c}"/>
    <br/>
        
        <aura:iteration items="{!v.EducationalDetailList}" var="item" indexVar="index">
        <c:Add_Educational_Details EducationalDetailListInnerComponent="{!v.EducationalDetailList}" IndexNo="{!index}"/>
        </aura:iteration>
     
    <lightning:button iconName="utility:add" variant="border-filled" label="Add Educational Details" onclick="{!c.addDetails}"></lightning:button>
        <br/>        
        <lightning:input type="checkbox" label="Are you available on weekends for Class" name="coursecheckbox" />
 
    <br/>
    <lightning:input aura:id="checkBox" type="checkbox" onchange="{!c.onCheckChange}" label="Are you interested in online course?" name="onlinechk"/>
     <aura:if isTrue="{!v.CheckBoxvalue}">
         <i>Happy Learning!</i>
    </aura:if>   
        
        <br/>
        
    <lightning:button type="Submitt" onclick="{!c.doSubmit}">Submitt</lightning:button>
        </div>
</aura:component>

Controller Code:
({
    doSubmit : function(cmp, evt, hlpr) {
        //call an apex function to store data in reg form
        //pass regform as paramamer which  you  have mentioned in attribute
        var RegForm = cmp.get("v.RegForm");
        var action = cmp.get("c.SaveRegistrationDetail");
        //set the paramamter  value
        action.setParams({ regForm  : RegForm });
        
        //set the callback  function
        action.setCallback(this, function(response) {
            var state = response.getState();
            if (state === "SUCCESS") {
                alert("From Server: " + response.getReturnValue());
                console.log("From Server:" + response.getReturnValue());
                
            }
           else if (state === "ERROR") {
                var errors = response.getError();
                if (errors) {
                    if (errors[0] && errors[0].message) {
                        console.log("Error message: " +
                                 errors[0].message);
                    }
                } else {
                    console.log("Unknown error");
                }
       
        // $A.enqueueAction adds the server-side action to the queue.
       
            }
        });
        $A.enqueueAction(action);  
        
    },
    
    onCheckChange: function(cmp,evt,hlpr) {
    console.log("this is  from controller Function");
        //function defined in helper section;
        
        hlpr.onClickCheckBoxHelper(cmp,event);
       },
    
    addDetails: function(cmp,evt,hlpr){
      console.log("Add educational Details");
      var currentEducationalDetailList = cmp.get("v.EducationalDetailList");
      var currentSize= parseInt((currentEducationalDetailList.length));
      var newSize= parseInt((currentSize.length)+1);
      currentEducationalDetailList.push(newSize);
      cmp.set("v.EducationalDetailList",currentEducationalDetailList);
    }
})
Apex Class:
public class SaveRegistrationFormDetails{
@AuraEnabled
public static id SaveRegistrationDetail(admtest__Registration_Form__c regForm ){
     // DML operation to save RegForm Details   
     insert regForm;
     return regForm.id; 
    
}
}

Are there ant issue with the namespace syntax  that  I  am using ?
It will be helpful if someone can guide me with this issue.
Thanks,
Ritu Ghosh