[gnome-usage] storage-actionbar: Null-check a variable before using it

[Adrien Plazas <aplazas src gnome org>]

commit 5cdc102cfb35d52055ca6640ef9b0b62b3991865
Author: Adrien Plazas <kekun plazas laposte net>
Date:   Fri Dec 3 12:28:42 2021 +0100

    storage-actionbar: Null-check a variable before using it
    
    This avoids a compilation warning.

 src/storage/storage-actionbar.vala | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)
---
diff --git a/src/storage/storage-actionbar.vala b/src/storage/storage-actionbar.vala
index 93a0da8..d471323 100644
--- a/src/storage/storage-actionbar.vala
+++ b/src/storage/storage-actionbar.vala
@@ -40,9 +40,13 @@ namespace Usage {
 
         [GtkCallback]
         private void delete_clicked() {
+            var application = GLib.Application.get_default() as Application;
             string display_message = _("Are you sure you want to permanently delete selected items?");
 
-            var dialog = new Gtk.MessageDialog ((GLib.Application.get_default() as 
Application).get_window(), Gtk.DialogFlags.MODAL,
+            if (application == null)
+                return;
+
+            var dialog = new Gtk.MessageDialog (application.get_window(), Gtk.DialogFlags.MODAL,
                 Gtk.MessageType.WARNING, Gtk.ButtonsType.OK_CANCEL, display_message);
             dialog.secondary_text = _("If you delete these items, they will be permanently lost.");