st-theme-node: Make sure that two NULL paint states are not equal

The comment clearly intended that for this to be the case, but a typo
prevented this from actually being done. This fixes the focused state
of the search field not working more than once.

https://bugzilla.gnome.org/show_bug.cgi?id=699799

src/st/st-theme-node.c

@@ -3821,7 +3821,7 @@ st_theme_node_paint_equal (StThemeNode *node,
 
   /* Make sure NULL != NULL */
   if (node == NULL || other == NULL)
-    return TRUE;
+    return FALSE;
 
   if (node == other)
     return TRUE;