[gnome-documents] toolbar: don't attempt to set an invalid document model

[Cosimo Cecchi <cosimoc src gnome org>]

commit 7ce516e72cbd8f326dafcb659dd33df50c7ca502
Author: Cosimo Cecchi <cosimoc gnome org>
Date:   Fri Sep 2 19:11:55 2011 -0400

    toolbar: don't attempt to set an invalid document model

 src/mainToolbar.js |    3 +++
 1 files changed, 3 insertions(+), 0 deletions(-)
---
diff --git a/src/mainToolbar.js b/src/mainToolbar.js
index b654582..6157bc8 100644
--- a/src/mainToolbar.js
+++ b/src/mainToolbar.js
@@ -201,6 +201,9 @@ MainToolbar.prototype = {
     },
 
     setModel: function(model, document) {
+        if (!this._model || !this._document)
+            return;
+
         this._model = model;
         this._document = document;