Editor crashes on AddWebsocketHost on other instance to he same port

1. Open project attached (or create a new project and add script to add websocket host (on certain port)) and run it in 2 Unity instances.
2. Press "Play" in both editors.

Actual result: Second Editor crashes:
8 com.unity3d.UnityEditor5.x 0x00000001020c0bc6 UNET::VirtualWsUserHost::~VirtualWsUserHost() + 54
9 com.unity3d.UnityEditor5.x 0x00000001020ae93c UNET::NetLibraryManager::AddWsHost(UNETHostTopology const, char const, int) + 428
10 com.unity3d.UnityEditor5.x 0x00000001020c6b91 NetworkTransport_CUSTOM_AddWsHostWrapper(MonoObject, MonoString, int) + 145

Expected result: Error appears with info that port is already occupied.