GUACAMOLE-2257: Clone mouse state object to reflect the state at the time of the event.

guacamole-common-js/src/main/webapp/modules/Mouse.js

@@ -546,10 +546,12 @@ Guacamole.Mouse.Event = function MouseEvent(type, state, events) {
 
     /**
      * The current mouse state at the time this event was fired.
+     * The state object is cloned so as not to be affected by subsequent events
+     * that will have their own dedicated Guacamole.Mouse.Event instance.
      *
      * @type {!Guacamole.Mouse.State}
      */
-    this.state = state;
+    this.state = { ...state };
 
     /**
      * @inheritdoc

guacamole/src/main/frontend/src/app/storage/services/localStorageService.js

@@ -121,6 +121,8 @@ angular.module('storage').provider('localStorageService', [function localStorage
 
         // Pull and parse value from internal storage, if present
         var data = storedItems[key];
+        if (!data || data === "undefined")
+            return null;
         if (data)
             return JSON.parse(data);