Fix crash if a DROP is attempted on an internally-dependent object.

Introduced in 8.4 rewrite of dependency.c.
Per bug #5072 from Amit Khandekar.

src/backend/catalog/dependency.c

@@ -8,7 +8,7 @@
  * Portions Copyright (c) 1994, Regents of the University of California
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/catalog/dependency.c,v 1.89.2.1 2009/08/07 15:28:07 tgl Exp $
+ *	  $PostgreSQL: pgsql/src/backend/catalog/dependency.c,v 1.89.2.2 2009/09/22 15:46:43 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -559,7 +559,8 @@ findDependentObjects(const ObjectAddress *object,
 				{
 					char	   *otherObjDesc;
 
-					if (object_address_present(&otherObject, pendingObjects))
+					if (pendingObjects &&
+						object_address_present(&otherObject, pendingObjects))
 					{
 						systable_endscan(scan);
 						/* need to release caller's lock; see notes below */

src/test/regress/expected/rules.out

@@ -1444,6 +1444,14 @@ insert into rule_and_refint_t3 values (1, 13, 11, 'row8');
 ERROR:  insert or update on table "rule_and_refint_t3" violates foreign key constraint "rule_and_refint_t3_id3a_fkey"
 DETAIL:  Key (id3a,id3b)=(1,13) is not present in table "rule_and_refint_t1".
 --
+-- disallow dropping a view's rule (bug #5072)
+--
+create view fooview as select 'foo'::text;
+drop rule "_RETURN" on fooview;
+ERROR:  cannot drop rule _RETURN on view fooview because view fooview requires it
+HINT:  You can drop view fooview instead.
+drop view fooview;
+--
 -- check for planner problems with complex inherited UPDATES
 --
 create table id (id serial primary key, name text);

src/test/regress/sql/rules.sql

@@ -851,6 +851,14 @@ create rule rule_and_refint_t3_ins as on insert to rule_and_refint_t3
 insert into rule_and_refint_t3 values (1, 11, 13, 'row7');
 insert into rule_and_refint_t3 values (1, 13, 11, 'row8');
 
+--
+-- disallow dropping a view's rule (bug #5072)
+--
+
+create view fooview as select 'foo'::text;
+drop rule "_RETURN" on fooview;
+drop view fooview;
+
 --
 -- check for planner problems with complex inherited UPDATES
 --