Improve state serialization

Change-Id: Ic9d9b791c548827028cbbd4c57751b0c88c8c265
diff --git a/dev/js/src/state/manager.js b/dev/js/src/state/manager.js
index 26cb482..6d7fe11 100644
--- a/dev/js/src/state/manager.js
+++ b/dev/js/src/state/manager.js
@@ -37,13 +37,17 @@
 
       
       
-      this._states = JSON.parse(value);
+      this._states = JSON.parse('{' + value + '}');
     },
 
 
     // Return the string representation of all states
     toString : function () {
-      return JSON.stringify(this._states);
+
+      if (this._states.size === 0)
+        return undefined;
+      
+      return JSON.stringify(this._states).slice(1,-1);
     },