js: make non-payload data more encoding-tolerant

--

* src/Helpers.js: As non-payload data might come in different
  encodings, a conversion has been introduced that worked in most
  cases. Data like the userid might come in different encodings,
  which we don't know of. For now, a try..catch returns the data
  as they are if the utf-8 decoding fails. Sometimes this yields the
  correct result, sometimes it may not work, but it won't stop the
  whole operation anymore.

lang/js/src/Helpers.js

@@ -115,7 +115,14 @@ export function isLongId (value){
  */
 export function decode (property){
     if (typeof property === 'string'){
+        try {
             return decodeURIComponent(escape(property));
+        }
+        catch (error){
+            if (error instanceof URIError) {
+                return property;
+            }
+        }
     } else if (Array.isArray(property)){
         let res = [];
         for (let arr=0; arr < property.length; arr++){