Schedules Apex Failing - Attempt to de-reference a null object

Question

I am getting the following error for a Scheduled Apex Job and don't know how to fix it (not a developer, just adapting some existing code). The aim is to update a field every night to trigger workflows, etc. I think the error could be around the field I want to update (as there are currently some records without a value in this field), but I could be wrong as the error mentions Object.

I've found similar queries but haven't figured out how to adapt answers for my specific case.

The full error is:

Scheduler: failed to execute scheduled job: jobId: 7071X000002o0om, class: common.apex.async.AsyncApexJobObject, reason: Attempt to de-reference a null object

Any suggestions of what to do / how to tweak the code greatly appreciated!

global class checkYoungPersonAllocations Implements Schedulable {

global void execute(SchedulableContext sc) {
    checkMyAllocations();
}

public void checkMyAllocations() {

    List<Young_Person_Allocation__c> affected = [SELECT Id, Name, Trigger_Field__c, Trip_Start_Date__c
                                 FROM Young_Person_Allocation__c
                                 WHERE Trip_Start_Date__c >= TODAY];

   for(Young_Person_Allocation__c thisAllocation : affected) {
       thisAllocation.Trigger_Field__c = thisAllocation.Trigger_Field__c + 1;
   }

  update affected;
}}

Answer 1

What I feel is, in your for loop, Trigger_Field__c is null. Null + 1 gives you NULL ptr exception. You have to do null check and then proceed.

global class checkYoungPersonAllocations Implements Schedulable {

global void execute(SchedulableContext sc) {
    checkMyAllocations();
}

public void checkMyAllocations() {

    List<Young_Person_Allocation__c> affected = [SELECT Id, Name, Trigger_Field__c, Trip_Start_Date__c
                                 FROM Young_Person_Allocation__c
                                 WHERE Trip_Start_Date__c >= TODAY];

   for(Young_Person_Allocation__c thisAllocation : affected) {
       if(thisAllocation.Trigger_Field__c!= null){
            thisAllocation.Trigger_Field__c = thisAllocation.Trigger_Field__c + 1;
       }else{
            thisAllocation.Trigger_Field__c =  1;

       } 
   }

  update affected;
}}