gui/date-chooser: Properly remove idle source

When disposing of the widget, also remove the associated idle source
that might exist. This prevents a crash.

Part-of: <https://gitlab.gnome.org/GNOME/gnome-calendar/-/merge_requests/742>

src/gui/common/gcal-date-chooser.c

@@ -66,7 +66,7 @@ struct _GcalDateChooser
   gboolean            show_events;
   gboolean            split_month_year;
 
-  gulong              update_indicators_idle_id;
+  unsigned int        update_indicators_idle_id;
 };
 
 static void          gcal_view_interface_init                    (GcalViewInterface  *iface);
@@ -873,6 +873,8 @@ gcal_date_chooser_finalize (GObject *object)
 {
   GcalDateChooser *self = GCAL_DATE_CHOOSER (object);
 
+  g_clear_handle_id (&self->update_indicators_idle_id, g_source_remove);
+
   g_clear_object (&self->model_signal_group);
 
   g_clear_pointer (&self->date, g_date_time_unref);