Error in chkpass.c (contrib area) with suggestion

Because author is not responding I'm writing to you.
In contrib/chkpass.c there is no checking against NULL values on input,
thus if you call eg. raw(NULL) then postgresql always dies.
Although storing encrypted password are highly required this behavior
makes this extension module unusable.

To correct it one must add some checkin before any PG_GETARG_XXX in
chkpass.c:
Suggested type of code follows:
------------------------------------------------------------------
 if(PG_ARGISNULL(0)) PG_RETURN_NULL();
------------------------------------------------------------------

Best regards and let me know if this is acceptable

Sedlak Anton