Use dash instead of underscore

src/iridium-window.ui

@@ -12,7 +12,7 @@
         <child>
           <object class="GtkToggleButton">
             <property name="visible">True</property>
-            <property name="action_name">win.preview</property>
+            <property name="action-name">win.preview</property>
             <child>
               <object class="GtkImage">
                 <property name="visible">True</property>