[gnome-photos] tracker-change-monitor: Guard against failure to resolve IDs

[Debarshi Ray <debarshir src gnome org>]

commit f5c2f517ad563f411600fa5d59fdbdc527e07049
Author: Debarshi Ray <debarshir gnome org>
Date:   Wed Sep 17 18:05:39 2014 +0200

    tracker-change-monitor: Guard against failure to resolve IDs
    
    I can't think of a reason why this will happen unless we are hitting
    some bug in Tracker, but it is happening in the wild. So let's guard
    against such scenarios.
    
    Fixes: https://bugzilla.gnome.org/735746

 src/photos-tracker-change-monitor.c |    5 +++++
 1 files changed, 5 insertions(+), 0 deletions(-)
---
diff --git a/src/photos-tracker-change-monitor.c b/src/photos-tracker-change-monitor.c
index a7cfe69..cb1b066 100644
--- a/src/photos-tracker-change-monitor.c
+++ b/src/photos-tracker-change-monitor.c
@@ -153,7 +153,12 @@ photos_tracker_change_monitor_send_events (PhotosTrackerChangeMonitor *self, GHa
       urn_id = photos_tracker_change_event_get_urn_id (change_event);
 
       predicate = (gchar *) g_hash_table_lookup (id_table, GINT_TO_POINTER (predicate_id));
+      if (G_UNLIKELY (predicate == NULL))
+        continue;
+
       urn = (gchar *) g_hash_table_lookup (id_table, GINT_TO_POINTER (urn_id));
+      if (G_UNLIKELY (urn == NULL))
+        continue;
 
       photos_tracker_change_event_set_resolved_values (change_event, urn, predicate);
       photos_tracker_change_monitor_add_event (self, change_event);