Update compatibility.md

For information: 

18:57:32.098 ERROR o.f.esl.client.inbound.Client[:469] - Error caught notifying listener of event [EslEvent: name=[CHANNEL_CREATE] headers=2, eventHeaders=130, eventBody=0 lines.]
java.lang.IllegalArgumentException: The state must not be null!
	at org.eclipse.smarthome.core.internal.events.EventPublisherImpl.postUpdate(EventPublisherImpl.java:122)
	at org.eclipse.smarthome.core.internal.events.EventPublisherImpl.postUpdate(EventPublisherImpl.java:179)
	at org.openhab.core.events.EventPublisherDelegate.postUpdate(EventPublisherDelegate.java:63)
	at org.openhab.binding.freeswitch.internal.FreeswitchBinding.newCallItemUpdate(FreeswitchBinding.java:375)
	at org.openhab.binding.freeswitch.internal.FreeswitchBinding.handleNewCallEvent(FreeswitchBinding.java:275)
	at org.openhab.binding.freeswitch.internal.FreeswitchBinding.eventReceived(FreeswitchBinding.java:169)
	at org.freeswitch.esl.client.inbound.Client$3$2.run(Client.java:465)
	at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1110)
	at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:603)
	at java.lang.Thread.run(Thread.java:722)