[gnome-photos] tracker-queue: Be more strict about what is acceptable

[Debarshi Ray <debarshir src gnome org>]

commit f220c2e7bffc51c71c3b9628fa71aa54c82165ab
Author: Debarshi Ray <debarshir gnome org>
Date:   Thu Jul 13 17:10:42 2017 +0200

    tracker-queue: Be more strict about what is acceptable

 src/photos-tracker-queue.c |    3 +++
 1 files changed, 3 insertions(+), 0 deletions(-)
---
diff --git a/src/photos-tracker-queue.c b/src/photos-tracker-queue.c
index 38feffd..dfbdd0b 100644
--- a/src/photos-tracker-queue.c
+++ b/src/photos-tracker-queue.c
@@ -286,6 +286,9 @@ photos_tracker_queue_initable_iface_init (GInitableIface *iface)
 PhotosTrackerQueue *
 photos_tracker_queue_dup_singleton (GCancellable *cancellable, GError **error)
 {
+  g_return_val_if_fail (cancellable == NULL || G_IS_CANCELLABLE (cancellable), NULL);
+  g_return_val_if_fail (error == NULL || *error == NULL, NULL);
+
   return g_initable_new (PHOTOS_TYPE_TRACKER_QUEUE, cancellable, error, NULL);
 }