Variable Wakeup-Time Sequence

Have it running with an echo dot.
Now I’m dealing with DateTime as data type, but this is brilliant:

The issue I face now: When I cancel the alarm or the alarm is executed:

2019-11-27 09:40:15.216 [vent.ItemStateChangedEvent] - Echo_Next_Alarm changed from 2019-11-27T09:40:00.000+0100 to UNDEF

I try to catch it in the rule:

	if (Echo_Next_Alarm.state == 'UNDEF') {
		logInfo("wakeup", "Timer cancelled")
	} else {

but get an error:

2019-11-27 09:40:15.227 [ERROR] [ntime.internal.engine.RuleEngineImpl] - Rule 'wakeup': d != java.lang.String