The FRM-40102: Record must be entered or deleted first happen when you try to edit a record and leave blank a required field and without saving it or deleting it, you try to move on to next record or database block. Better you first cancel the operation if you dont want to complete the transaction.
Oracle Form's error information
Cause: You pressed [Next Record] or [Down] in a context where it is meaningless. Either:
1. The last record in a block is the current record.
2. The block is empty.
3. You are in a new record in the middle of the block created by pressing [Insert Record].
Action: No action is necessary.