Call FDW validator functions even when the options list is empty.

This is useful since a validator might want to require certain options
to be provided.  The passed array is an empty text array in this case.

Per suggestion by Laurenz Albe, though this is not quite his patch.

src/backend/commands/foreigncmds.c

@@ -165,8 +165,18 @@ transformGenericOptions(Oid catalogId,
 
 	result = optionListToArray(resultOptions);
 
-	if (OidIsValid(fdwvalidator) && DatumGetPointer(result) != NULL)
-		OidFunctionCall2(fdwvalidator, result, ObjectIdGetDatum(catalogId));
+	if (OidIsValid(fdwvalidator))
+	{
+		Datum	valarg = result;
+
+		/*
+		 * Pass a null options list as an empty array, so that validators
+		 * don't have to be declared non-strict to handle the case.
+		 */
+		if (DatumGetPointer(valarg) == NULL)
+			valarg = PointerGetDatum(construct_empty_array(TEXTOID));
+		OidFunctionCall2(fdwvalidator, valarg, ObjectIdGetDatum(catalogId));
+	}
 
 	return result;
 }