Steps to reproduce:
1. Download and import attached project "login.zip"
2. Open and play scene "Server"
3. Notice that another command line window appears. Switch focus multiple times by clicking anywhere on new window and then back on Unity
4. Unity crashes

Expected result: Unity not to crash.

Note: Sometimes it crashes almost immediately, but sometimes it needs quite a bit of clicking back and forth.

Windows 10
Unity 5.1.4f1, 5.2.4f1, 5.3.0f4, 5.4.0a6, 5.4.0b1

Note: For some reason, there were instances that it did not crash on 5.4.0a6