background: Come up with 'Wallpapers' selected and displayed

https://bugzilla.gnome.org/show_bug.cgi?id=630417

panels/background/background.ui

@@ -70,7 +70,6 @@
           <object class="GtkComboBox" id="sources-combobox">
             <property name="visible">True</property>
             <property name="model">sources-liststore</property>
-            <property name="active">0</property>
             <child>
               <object class="GtkCellRendererText" id="cellrenderertext2"/>
               <attributes>

panels/background/cc-background-panel.c

@@ -676,6 +676,9 @@ cc_background_panel_init (CcBackgroundPanel *self)
   widget = WID ("sources-combobox");
   g_signal_connect (widget, "changed", G_CALLBACK (source_changed_cb), priv);
 
+  /* select first item */
+  gtk_combo_box_set_active (GTK_COMBO_BOX (widget), 0);
+
   /* connect to the background iconview change signal */
   widget = WID ("backgrounds-iconview");
   g_signal_connect (widget, "selection-changed",