html10n.js: Don't break in getDirection if language hasn't been set

fixes #1724

src/static/js/html10n.js

@@ -900,6 +900,7 @@ window.html10n = (function(window, document, undefined) {
    * Returns the direction of the language returned be html10n#getLanguage
    */
   html10n.getDirection = function() {
+    if(!this.language) return
     var langCode = this.language.indexOf('-') == -1? this.language : this.language.substr(0, this.language.indexOf('-'))
     return html10n.rtl.indexOf(langCode) == -1? 'ltr' : 'rtl'
   }