Steps to reproduce:
1) Make sure you have a second monitor attached.
2) Open any project in Unity.
3) Place Unity window in the second monitor.
4) Unplug the monitor.

The editor window becomes black with some squares and artefacts of the editor window in them.
Going to Window > Layouts and selecting any layout restores the editor.

This does not occur when the editor is in Metal mode.

Reproduced on:
2017.1.0b4, 5.6.1f1, 5.5.3p2, 5.4.5p1, 5.4.0f3

Did not reproduce:
5.3.8f1

Device:
Macbook Pro Early 2013 w/ Nvidia 650M and 1080p monitor