[gnome-documents] main-toolbar: reset collection back button state on toolbar clear

[Cosimo Cecchi <cosimoc src gnome org>]

commit c3a4145e5ab96910be547fbbcd3764c0c3dcd514
Author: Cosimo Cecchi <cosimoc gnome org>
Date:   Tue Jun 26 13:41:04 2012 -0400

    main-toolbar: reset collection back button state on toolbar clear

 src/mainToolbar.js |    1 +
 1 files changed, 1 insertions(+), 0 deletions(-)
---
diff --git a/src/mainToolbar.js b/src/mainToolbar.js
index 72bb740..7c9139c 100644
--- a/src/mainToolbar.js
+++ b/src/mainToolbar.js
@@ -120,6 +120,7 @@ const MainToolbar = new Lang.Class({
 
     _clearStateData: function() {
         this._model = null;
+        this._collBackButton = null;
 
         if (this._collectionId != 0) {
             Global.collectionManager.disconnect(this._collectionId);