cally-util: Don't free a NULL pointer

The only place key_event can not be NULL is in this branch.
Spotted by Coverity.

https://bugzilla.gnome.org/show_bug.cgi?id=689496

clutter/cally/cally-util.c

@@ -358,10 +358,10 @@ cally_key_snooper (ClutterActor *actor,
       /* func data is inside the hash table */
       consumed = g_hash_table_foreach_steal (new_hash, notify_hf, key_event);
       g_hash_table_destroy (new_hash);
-    }
 
       g_free (key_event->string);
       g_free (key_event);
+    }
 
   return (consumed ? 1 : 0);
 }