[gtk] Fix the modelbutton demo _again_

[Matthias Clasen <matthiasc src gnome org>]

commit 422262436b8604a97cbd90a7f673caea54571025
Author: Matthias Clasen <mclasen redhat com>
Date:   Mon Apr 30 20:09:57 2018 -0400

    Fix the modelbutton demo _again_
    
    It lost the action-target properties again.

 demos/gtk-demo/modelbutton.ui | 3 +++
 1 file changed, 3 insertions(+)
---
diff --git a/demos/gtk-demo/modelbutton.ui b/demos/gtk-demo/modelbutton.ui
index 71309052f9..da74fdba0b 100644
--- a/demos/gtk-demo/modelbutton.ui
+++ b/demos/gtk-demo/modelbutton.ui
@@ -56,6 +56,7 @@
         <child>
           <object class="GtkModelButton">
             <property name="action-name">win.color</property>
+            <property name="action-target">'red'</property>
             <property name="text">Red</property>
             <property name="inverted">1</property>
           </object>
@@ -63,6 +64,7 @@
         <child>
           <object class="GtkModelButton">
             <property name="action-name">win.color</property>
+            <property name="action-target">'green'</property>
             <property name="text">Green</property>
             <property name="inverted">1</property>
           </object>
@@ -70,6 +72,7 @@
         <child>
           <object class="GtkModelButton">
             <property name="action-name">win.color</property>
+            <property name="action-target">'blue'</property>
             <property name="text">Blue</property>
             <property name="inverted">1</property>
           </object>