[gnome-games] ui: Check there is a media set before updating it

[Adrien Plazas <aplazas src gnome org>]

commit d1cde2b39c54d74a92b547c4992a659d15c1d09a
Author: Adrien Plazas <kekun plazas laposte net>
Date:   Wed Sep 28 14:37:28 2016 +0200

    ui: Check there is a media set before updating it
    
    This avoids a runtime critial error.
    
    https://bugzilla.gnome.org/show_bug.cgi?id=772118

 src/ui/media-selector.vala |    4 ++++
 1 files changed, 4 insertions(+), 0 deletions(-)
---
diff --git a/src/ui/media-selector.vala b/src/ui/media-selector.vala
index 9c0c031..ab320d7 100644
--- a/src/ui/media-selector.vala
+++ b/src/ui/media-selector.vala
@@ -23,6 +23,10 @@ private class Games.MediaSelector : Gtk.Popover {
 
        private void update_media () {
                var media_number = 0;
+
+               if (_media_set == null)
+                       return;
+
                _media_set.foreach_media ((media) => {
                        string media_name;
                        if (media.title == null)