FRM-40735: WHEN-NEW-RECORD-INSTANCE trigger raised unhandled exception ORA-06502.

Dear Community,

I have an CUSTOM.pll in my instance.  And I added just a very basic validation condition in the event procedure of CUSTOM.pll  -

  v_ven_name   PO_HEADERS.ATTRIBUTE5%TYPE;

  begin

    IF event_name='WHEN-NEW-RECORD-INSTANCE' THEN

     IF form_name='POXPOEPO' AND block_name='PO_HEADERS' THEN

      v_ven_name := NAME_IN(':PO_HEADERS.ATTRIBUTE5');

      IF name_in(':PO_HEADERS.ATTRIBUTE15') = 'PARTNER' THEN

       FND_MESSAGE.DEBUG('This Purchase Order is pending with '||v_ven_name);

      END IF;

     END IF;

    END IF; 

  end event;

And compiled the .pll after placing in $AU_TOP/resource.  And when I open the forms, I run into the below issue at the beginning of the form based applications -