pgsql-server: Fix a couple of small errors in trigger-list management,

Log Message:
-----------
Fix a couple of small errors in trigger-list management, as per recent
discussion.

Modified Files:
--------------
pgsql-server/src/backend/commands:
trigger.c (r1.169 -> r1.170)
(http://developer.postgresql.org/cvsweb.cgi/pgsql-server/src/backend/commands/trigger.c.diff?r1=1.169&r2=1.170)