Symptom:
Re-assign button is not working on configure destination cluster when user needs to re-assign the virtual machine. Getting the following error from firebug when clicking Re-assign. 

Error executing: function (e){if(this._onClick(e)===false){e.preventDefault();}else{if(this.type=="submit"&&!this.focusNode.form){for(var _1=this.domNode;_1.parentNode;_1=_1.parentNode){var _2=dijit.byNode(_1);if(_2&&typeof _2._onSubmit=="function"){_2._onSubmit(e);break;}}}}}
TypeError: _28[key] is null
	
(23 out of range 16)

Also, this would cause user to not be able to save or crate a new destination migration destination cluster even after a new VM (not duplicated VM) is reassigned to a destination node.

Conditions:
Cluster has at least two nodes. Select the same VM as it was selected for a previous destination node.