[tracker] tracker-store: Fix critical warning in case of syntax error in query

[Philip Van Hoof <pvanhoof src gnome org>]

commit f3cbf7ce1e6e0d9185ffd8577abe34ab2ea98bb0
Author: Philip Van Hoof <philip codeminded be>
Date:   Thu Apr 29 22:08:28 2010 +0200

    tracker-store: Fix critical warning in case of syntax error in query

 src/tracker-store/tracker-store.c |    3 ++-
 1 files changed, 2 insertions(+), 1 deletions(-)
---
diff --git a/src/tracker-store/tracker-store.c b/src/tracker-store/tracker-store.c
index 542ce7e..7dda0b4 100644
--- a/src/tracker-store/tracker-store.c
+++ b/src/tracker-store/tracker-store.c
@@ -425,7 +425,8 @@ pool_dispatch_cb (gpointer data,
 
 		task->data.query.thread_data = task->callback.query.in_thread (cursor, task->error, task->user_data);
 
-		g_object_unref (cursor);
+		if (cursor)
+			g_object_unref (cursor);
 		task->data.query.running_thread = NULL;
 
 	} else if (task->type == TRACKER_STORE_TASK_TYPE_UPDATE) {