[libdazzle/libdazzle-3-26] menu: relax menu-id requirement

[Christian Hergert <chergert src gnome org>]

commit 9043eba33ba0400ae9f2def5cc28291bac710e34
Author: Christian Hergert <chergert redhat com>
Date:   Sun Oct 22 16:35:41 2017 -0700

    menu: relax menu-id requirement
    
    We can allow NULL here and just clear the menu.

 src/menus/dzl-menu-button.c |    6 ++++++
 1 files changed, 6 insertions(+), 0 deletions(-)
---
diff --git a/src/menus/dzl-menu-button.c b/src/menus/dzl-menu-button.c
index f1c2ac3..fbdae7e 100644
--- a/src/menus/dzl-menu-button.c
+++ b/src/menus/dzl-menu-button.c
@@ -189,6 +189,12 @@ dzl_menu_button_set_menu_id (DzlMenuButton *self,
 
   g_return_if_fail (DZL_IS_MENU_BUTTON (self));
 
+  if (menu_id == NULL)
+    {
+      dzl_menu_button_set_model (self, NULL);
+      return;
+    }
+
   app = g_application_get_default ();
 
   if (DZL_IS_APPLICATION (app))