[gnome-games] ui: Fix "Source ID was not found when attempting to remove it"

[Adrien Plazas <aplazas src gnome org>]

commit 802505dcf04e234e5fcc22ed2ac1dde066d9641b
Author: Adrien Plazas <kekun plazas laposte net>
Date:   Sat Aug 27 12:05:35 2016 +0200

    ui: Fix "Source ID was not found when attempting to remove it"
    
    Reset the fullscreen activity source ID after removing it to avoid
    trying to remove it several times.
    
    https://bugzilla.gnome.org/show_bug.cgi?id=770491

 src/ui/display-box.vala |    4 +++-
 1 files changed, 3 insertions(+), 1 deletions(-)
---
diff --git a/src/ui/display-box.vala b/src/ui/display-box.vala
index 166b03b..9cb4026 100644
--- a/src/ui/display-box.vala
+++ b/src/ui/display-box.vala
@@ -77,8 +77,10 @@ private class Games.DisplayBox : Gtk.EventBox {
        }
 
        private void on_activity () {
-               if (timeout_id != -1)
+               if (timeout_id != -1) {
                        Source.remove ((uint) timeout_id);
+                       timeout_id = -1;
+               }
 
                if (!is_fullscreen)
                        return;