App is crashing after disconnecting and reconnecting

[FrazerSeymour]

Steps to reproduce:

• Connect to a wifi-hotspot as wifi-client. (connects succesfully)
• Disconnect by closing the app and tapping "Go offline" in the notification (other phones see disappear from online users list)
• Re-start the app and reconnect (app crashes, following appears in the .mesh thread:)

02-26 10:59:22.910 13735-15798/.mesh E/AndroidRuntime: FATAL EXCEPTION: Thread-757
Process: .mesh, PID: 13735
java.lang.NullPointerException: Attempt to invoke virtual method 'int java.lang.Object.hashCode()' on a null object reference
    at java.util.concurrent.ConcurrentHashMap.get(ConcurrentHashMap.java:772)
    at io.left.rightmesh.android.MeshService.b(SourceFile:1005)
    at io.left.rightmesh.mesh.h.g(SourceFile:25733)
    at io.left.rightmesh.mesh.h$6.run(SourceFile:1389)