Added data === 'object' to check if data is an object before parsing

the content. This avoid parsing data that is not useful, like in
situations where pinging a file that doesn’t exist return index.html.

Author: pokono

src/catalog.js

@@ -109,8 +109,10 @@ angular.module('gettext').factory('gettextCatalog', function (gettextPlurals, $h
                 url: url,
                 cache: catalog.cache
             }).success(function (data) {
-                for (var lang in data) {
-                    catalog.setStrings(lang, data[lang]);
+                if (typeof data === 'object') {
+                    for (var lang in data) {
+                        catalog.setStrings(lang, data[lang]);
+                    }
                 }
             });
         }