Can't reproduce this and got this only once for now.

1 Basic Networking(Multiplayer) project was opened in Editor
2 I built Standalone and ran it
3 Pressed Play in Editor
4 Did some actions in Standalone(like Creating Internet Match) - but this could not influence the Editor because it was not connected to any Internet Match yet
5 Started to do actions in Editor (so it's window became focused) and tried to open some tab in Connect window (I believe Multiplayer tab)

Actual result: crash
========== OUTPUTING STACK TRACE ==================

0x0000000140CAE861 (Unity) UnityConnectStateMachine::RefreshUserAndOrganizations
0x0000000140CB0091 (Unity) UnityConnectStateMachine::Tick
0x0000000140CAAA25 (Unity) UnityConnect::Tick
0x0000000140BBD673 (Unity) Application::TickTimer
0x0000000140DFC3DC (Unity) FindMonoBinaryToUse
0x0000000140DFDA19 (Unity) WinMain
0x00000001415A6CF4 (Unity) read
0x0000000076BC59CD (kernel32) BaseThreadInitThunk

========== END OF STACKTRACE ===========