Issue

Error 37 - Attempt to dereference a null object encountered when entering the grading wizard. 

Possible Reasons

1. There are no Students enrolled into the current Session thus displaying no records and the error pops up.
2. The User does not have record access to the Students Session Connection in order to take their attendance.

Possible Resolution

Navigate to Setup > Digital Experience > Settings. Check the sharing sets setting. For example, the sharing sets are determined by the user's account field ‘redu_Community_Sharing_Account__c’. This means that only users under the account with this field set up correctly will have access. 

Go to the related field (e.g., the account field in the example above) and update it with the correct setup.