Keep plugin state in state manager (fixes #201)

Change-Id: If4a5305f3e41f1fcac4a47afeba613b3106c69fa
diff --git a/dev/js/src/state/manager.js b/dev/js/src/state/manager.js
index 339503d..136310b 100644
--- a/dev/js/src/state/manager.js
+++ b/dev/js/src/state/manager.js
@@ -33,9 +33,9 @@
 
     // Parse a value and populate states
     _parse : function (value) {
-      if (value === undefined || value === '')
+      if (value == null || value == undefined || value == '')
         return;
-      
+
       this._states = JSON.parse('{' + value + '}');
     },
 
@@ -52,7 +52,7 @@
 
     // Update the query component for states
     _update : function () {
-      this._e.value = this.toString();
+      this._e.setAttribute("value", this.toString());
     },
 
 
@@ -63,6 +63,11 @@
       const t = this;
       let s = stateClass.create(values);
 
+      if (this._states[name] != undefined) {
+        if (values.includes(this._states[name]))
+          s.setIfNotYet(this._states[name]);
+      };
+
       // Set default value
       // TODO: It would be better to make this part
       // of the state and serialize correctly using TOJSON()