[simple-scan] Fix scan menu not working Unity/XFCE/MATE etc

[Robert Ancell <rancell src gnome org>]

commit 87ea7a6603051720faf2d43b28dd04dbefb5ac55
Author: Robert Ancell <robert ancell canonical com>
Date:   Tue Jun 6 22:19:33 2017 +1200

    Fix scan menu not working Unity/XFCE/MATE etc

 src/app-window.ui |    1 +
 1 files changed, 1 insertions(+), 0 deletions(-)
---
diff --git a/src/app-window.ui b/src/app-window.ui
index e5d6cad..bbdf1c7 100644
--- a/src/app-window.ui
+++ b/src/app-window.ui
@@ -522,6 +522,7 @@
                 <property name="label" translatable="yes" comments="Label on scan toolbar 
item">Scan</property>
                 <property name="use_underline">True</property>
                 <property name="icon_name">scanner</property>
+                <property name="menu">scan_button_menu</property>
                 <signal name="clicked" handler="scan_button_clicked_cb" swapped="no"/>
               </object>
               <packing>