Email Response - impact of the actions for implementing : "Cannot Insert Null Into Audit Trail Table

From Activities screen, if you drill down on an Activity of Type "Email - Outbound", and click on "Reply All" Button, the Outgoing Message form becomes editable.
Then to Cancel this Outgoing Message, we need to click on "Cancel Send" from Menu (Menu -> Cancel Send). On doing so, we get the below error message.


[1] An error has occurred while deleting the record.

Please try to delete again.(SBL-DAT-00236)
[2] An error has occurred writing to a record.

Please continue or ask your systems administrator to check your application configuration if the problem persists.(SBL-DBC-00111)
[3] ORA-01400: cannot insert NULL into ("SIEBEL"."S_AUDIT_ITEM"."ITEM_IDEN_NUM")