multi-choice: Fix endless timeout

There are two mapped events for each back/forward buttons in this
widget: button-press and button-release.

When you reach the limits like January and December, button-release is
lost, and you don't get it anymore. That caused button_timeout function
to not be disable anymore, so it's kept in loop forever.

This code fix checks in button_timeout function if any of the back/
forward buttons are still mapped. If not, it prevents from calling
button_timout, stopping the loop.

https://bugzilla.gnome.org/show_bug.cgi?id=776459

src/gcal-multi-choice.c

@@ -187,6 +187,15 @@ button_timeout (gpointer user_data)
   if (self->click_id == 0)
     return G_SOURCE_REMOVE;
 
+  if (!gtk_widget_get_mapped (self->down_button) && !gtk_widget_get_mapped (self->up_button))
+    {
+      if (self->click_id)
+        g_source_remove (self->click_id);
+      self->click_id = 0;
+      self->active = NULL;
+      return G_SOURCE_REMOVE;
+    }
+
   res = button_activate (self, self->active);
   if (!res)
     {