Added space to console warning

lib/DataSet.js

@@ -264,7 +264,7 @@ DataSet.prototype.update = function (data, senderId) {
       if (data[i] instanceof Object){
         addOrUpdate(data[i]);
       } else {
-        console.warn("Ignoring input item, which is not an object at index"+i);
+        console.warn('Ignoring input item, which is not an object at index ' + i);
       }
     }
   }