[gnome-documents] Fix error when goa dies

[William Jon McCann <mccann src gnome org>]

commit 9f1212d18b95d86090ea29e80140b8539e3bffa1
Author: William Jon McCann <jmccann redhat com>
Date:   Sat Feb 16 17:31:15 2013 -0500

    Fix error when goa dies
    
    https://bugzilla.gnome.org/show_bug.cgi?id=693956

 src/manager.js |    3 +--
 1 files changed, 1 insertions(+), 2 deletions(-)
---
diff --git a/src/manager.js b/src/manager.js
index 114034c..1a9d08c 100644
--- a/src/manager.js
+++ b/src/manager.js
@@ -288,8 +288,7 @@ const BaseView = new Lang.Class({
 
     _visibilityForHeading: function(col, cell, model, iter, visible, additionalFunc) {
         let heading = model.get_value(iter, BaseModelColumns.HEADING_TEXT);
-
-        if ((visible && heading.length) || (!visible && !heading.length))
+        if ((visible && heading != null && heading.length) || (!visible && heading != null && 
!heading.length))
             cell.visible = true;
         else
             cell.visible = false;