[gnome-calendar] application: Add weak ref to window

[Georges Basile Stavracas Neto <gbsneto src gnome org>]

commit 7bf8d8851b12af28e168f57110e98077e8a16770
Author: Georges Basile Stavracas Neto <georges stavracas gmail com>
Date:   Mon Aug 16 19:47:54 2021 -0300

    application: Add weak ref to window

 src/gui/gcal-application.c | 1 +
 1 file changed, 1 insertion(+)
---
diff --git a/src/gui/gcal-application.c b/src/gui/gcal-application.c
index 84e38b6d..f57257d5 100644
--- a/src/gui/gcal-application.c
+++ b/src/gui/gcal-application.c
@@ -391,6 +391,7 @@ gcal_application_activate (GApplication *application)
                                     NULL);
 
       g_signal_connect (self->window, "destroy", G_CALLBACK (gtk_widget_destroyed), &self->window);
+      g_object_add_weak_pointer (G_OBJECT (self->window), (gpointer*) &self->window);
       gtk_widget_show (self->window);
     }