[gnome-calendar] Repair application icon

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

commit 3f42719ebe9c020be5424034847bbf9db80377e6
Author: Ralph Plawetzki <ralph purejava org>
Date:   Tue Sep 25 12:33:53 2018 +0200

    Repair application icon
    
    Fixes #306

 src/gcal-application.c | 2 ++
 1 file changed, 2 insertions(+)
---
diff --git a/src/gcal-application.c b/src/gcal-application.c
index cf62c196..9037dc32 100644
--- a/src/gcal-application.c
+++ b/src/gcal-application.c
@@ -350,6 +350,8 @@ gcal_application_startup (GApplication *app)
 
   self = GCAL_APPLICATION (app);
 
+  gtk_window_set_default_icon_name ("org.gnome.Calendar");
+
   /* add actions */
   g_action_map_add_action_entries (G_ACTION_MAP (app),
                                    gcal_app_entries,