launcher: Handle GApplication::activate

GApplication warns if you do not handle activate.

For now this does nothing, typically it would focus the main window
of an application, which doesn't apply to many of Cog's platforms.

(cherry picked from commit 5976f59)

launcher/cog-launcher.c

@@ -436,6 +436,14 @@ cog_launcher_startup(GApplication *application)
 #endif
 }
 
+static void
+cog_launcher_activate(GApplication *application)
+{
+    /* GApplication warns if activate is not handled. Usually this signal will focus a
+       window but this doesn't apply to many of our platforms so this is a noop. */
+    G_APPLICATION_CLASS(cog_launcher_parent_class)->activate(application);
+}
+
 static void
 cog_launcher_shutdown(GApplication *application)
 {
@@ -1406,6 +1414,7 @@ cog_launcher_class_init(CogLauncherClass *klass)
     application_class->startup = cog_launcher_startup;
     application_class->shutdown = cog_launcher_shutdown;
     application_class->handle_local_options = cog_launcher_handle_local_options;
+    application_class->activate = cog_launcher_activate;
 
     g_object_class_install_property(object_class,
                                     PROP_AUTOMATED,