[gnome-boxes] media-manager: fix crash when tracker is not available

[Zeeshan Ali Khattak <zeeshanak src gnome org>]

commit f0d5f652b392e0e47f7d79f4315c4ca5d66012e9
Author: Olivier Blin <dev blino org>
Date:   Wed Oct 10 20:21:25 2012 +0200

    media-manager: fix crash when tracker is not available
    
    https://bugzilla.gnome.org/show_bug.cgi?id=685905

 src/media-manager.vala |    3 +++
 1 files changed, 3 insertions(+), 0 deletions(-)
---
diff --git a/src/media-manager.vala b/src/media-manager.vala
index 7159c3a..7e96520 100644
--- a/src/media-manager.vala
+++ b/src/media-manager.vala
@@ -57,6 +57,9 @@ private class Boxes.MediaManager : Object {
             }
         }
 
+        if (connection == null)
+            return list;
+
         // Now ISO files
         try {
             var cursor = yield connection.query_async (SPARQL_QUERY);