Set owner script - graceful way to not execute?

I have successfully built a script that sets the Owned by attribute based on the value selected in an enumeration.  I then wanted to have it also check a boolean attribute and if that boolean is false, to NOT set the Owned by field, but to let the user set it.  I have this working, but not gracefully.

Below is a snippet of the code.  For the "else" condition I am simply returning an empty string instead of a UUID.  This has the intended effect - the Owned by attribute is not set automatically, but it of course results in a null pointer exception.  I was wondering if there was a better way to accomplish this so as not to throw an error?


(function() {
var WorkItemAttributes= com.ibm.team.workitem.api.common.WorkItemAttributes;

var SetECMOwner= dojo.declare("org.example.SetECMOwner", null, {

    getValue: function(attributeId, workItem, configuration) {

    // retrieve state of auto-assign attribute
    var autoAssign = workItem.getValue("delegateflag");
    // if auto-assign is turned on (by default), execute the body of the script
    if (autoAssign == true ) {
       DO SOME STUFF;
       return UUID
   }
   else {
       return "";
   }