[#258,model][xs]: tiny bugfix for cases where fields in raw state contain a non-string - fixes #258.

src/model.js

@@ -105,11 +105,12 @@ my.Dataset = Backbone.Model.extend({
     } 
 
     // fields is an array of strings (i.e. list of field headings/ids)
-    if (fields && fields.length > 0 && typeof fields[0] === 'string') {
+    if (fields && fields.length > 0 && typeof(fields[0]) != 'object') {
       // Rename duplicate fieldIds as each field name needs to be
       // unique.
       var seen = {};
       fields = _.map(fields, function(field, index) {
+        field = field.toString();
         // cannot use trim as not supported by IE7
         var fieldId = field.replace(/^\s+|\s+$/g, '');
         if (fieldId === '') {