gtktiledviewer: provide activation function

This fixes the gtktiledviewer on some distros/gtk
versions that require an activation function to be
provided.

Change-Id: I95fb3ed4e92e27d9c725ca38b4cb5a4f8af51771
Reviewed-on: https://gerrit.libreoffice.org/71588Reviewed-by: Jan Holesovsky <kendy@collabora.com>
Tested-by: Jan Holesovsky <kendy@collabora.com>

libreofficekit/qa/gtktiledviewer/gtv-application.cxx

@@ -27,6 +27,12 @@ getPrivate(GtvApplication* app)
     return static_cast<GtvApplicationPrivate*>(gtv_application_get_instance_private(app));
 }
 
+static void
+gtv_application_activate(GApplication*)
+{
+    // If this isn't provided, some GTK versions fail to run us at all.
+}
+
 static void
 gtv_application_open(GApplication* app, GFile** file, gint /*nFiles*/, const gchar* /*hint*/)
 {
@@ -142,6 +148,7 @@ gtv_application_handle_local_options(GApplication* app, GVariantDict* options)
 static void
 gtv_application_class_init(GtvApplicationClass* klass)
 {
+    G_APPLICATION_CLASS(klass)->activate = gtv_application_activate;
     G_APPLICATION_CLASS(klass)->open = gtv_application_open;
     G_APPLICATION_CLASS(klass)->handle_local_options = gtv_application_handle_local_options;
     G_OBJECT_CLASS(klass)->dispose = gtv_application_dispose;