NPE spotted in mediator logs

[BarDweller]

[3/8/18 12:55:20:884 UTC] 0001abef id=         org.gameontext.mediator                                      I : ae611df2 : C    M <- R : player,*,{"type":"chat","username":"The ugly monster","content":"I am still alive!","bookmark":"not-bookmarked"}
[3/8/18 12:55:20:884 UTC] 0001abef id=         org.gameontext.mediator                                      W : 815ed5c4 : Uncaught exception handling client-bound message
java.lang.NullPointerException
	at org.gameontext.mediator.MediatorNexus$SingleUserView.stillConnected(MediatorNexus.java:669)
	at org.gameontext.mediator.MediatorNexus$SingleUserView.sendToClients(MediatorNexus.java:660)
	at org.gameontext.mediator.room.WebSocketClientConnection$1.onMessage(WebSocketClientConnection.java:135)
	at org.gameontext.mediator.room.WebSocketClientConnection$1.onMessage(WebSocketClientConnection.java:125)
	at com.ibm.ws.wsoc.LinkRead.processWithWholeMessageHandler(LinkRead.java:639)
	at com.ibm.ws.wsoc.LinkRead.processRead(LinkRead.java:335)
	at com.ibm.ws.wsoc.WsocConnLink.processRead(WsocConnLink.java:990)
	at com.ibm.ws.wsoc.WsocReadCallback.completeLogic(WsocReadCallback.java:61)
	at com.ibm.ws.wsoc.WsocReadCallback.complete(WsocReadCallback.java:47)
	at com.ibm.ws.tcpchannel.internal.WorkQueueManager.requestComplete(WorkQueueManager.java:501)
	at com.ibm.ws.tcpchannel.internal.WorkQueueManager.attemptIO(WorkQueueManager.java:571)
	at com.ibm.ws.tcpchannel.internal.WorkQueueManager.workerRun(WorkQueueManager.java:926)
	at com.ibm.ws.tcpchannel.internal.WorkQueueManager$Worker.run(WorkQueueManager.java:1015)
	at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1160)
	at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:635)
	at java.lang.Thread.run(Thread.java:811)

[BarDweller]

Might be a dupe of #48 ?