Fix bug on info pages for Shows.

Return error parameter to Datatables on exception.
Return draw counter to Datatables.

data/interfaces/default/info.html

@@ -263,7 +263,7 @@ from plexpy import helpers
             type: 'post',
             data: function ( d ) {
                 return { 'json_data': JSON.stringify( d ),
-                         'grandparent_rating_key': ${data['grandparent_rating_key']}
+                         'grandparent_rating_key': ${data['rating_key']}
                 };
             }
         }