[gnome-documents] preview: fix check for open action sensitivity

[Cosimo Cecchi <cosimoc src gnome org>]

commit 2dfa5228af29237343976365e0c3efccc1f78ce2
Author: Cosimo Cecchi <cosimoc gnome org>
Date:   Sun Oct 30 22:11:31 2016 -0700

    preview: fix check for open action sensitivity
    
    We have to use the app name, since the default app may not be there for
    web documents.

 src/preview.js |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)
---
diff --git a/src/preview.js b/src/preview.js
index f679d86..a387dea 100644
--- a/src/preview.js
+++ b/src/preview.js
@@ -187,7 +187,7 @@ const Preview = new Lang.Class({
         this._spinner.stop();
 
         this.set_visible_child_name('view');
-        this.getAction('open-current').enabled = (doc.defaultApp != null);
+        this.getAction('open-current').enabled = (doc.defaultAppName != null);
     },
 
     onLoadError: function(manager, doc, message, exception) {