[dconf] only check anti-expose if non-NULL

[Ryan Lortie <ryanl src gnome org>]

commit bfef76adfd833257d936ad0f7f6e92f36a4c00a1
Author: Ryan Lortie <desrt desrt ca>
Date:   Mon Jun 21 12:03:18 2010 -0400

    only check anti-expose if non-NULL

 engine/dconf-engine.c |    9 ++++++---
 1 files changed, 6 insertions(+), 3 deletions(-)
---
diff --git a/engine/dconf-engine.c b/engine/dconf-engine.c
index 14ed5d2..2122f0d 100644
--- a/engine/dconf-engine.c
+++ b/engine/dconf-engine.c
@@ -252,9 +252,12 @@ dconf_engine_decode_notify (DConfEngine   *engine,
 
   g_variant_get_child (body, 0, "t", &seqno);
 
-  ae = dconf_engine_make_tag (bus_type, sender, seqno);
-  matched = strcmp (ae, anti_expose) == 0;
-  g_free (ae);
+  if (anti_expose)
+    {
+      ae = dconf_engine_make_tag (bus_type, sender, seqno);
+      matched = strcmp (ae, anti_expose) == 0;
+      g_free (ae);
+    }
 
   if (matched)
     return FALSE;