[OSX 10.13][2018.1] Rapidly switching between 2 game view tabs multiple times may freeze or crash the editor when rendering with Metal.
Note: it's much harder to reproduce on the latest 10.13.4 Beta (17E160e)

To reproduce:
1. Open project
2. Open scene
3. Switch between game view tabs multiple times(gif attached)

Expected: tabs will be switched multiple times
Actual: after a few times switching between tabs, one tab 'disappears' and editor freezes

Reproduced: 2017.2x, 2017.3x, 2018.1.0a1, 2018.1.0b4
Not reproducible: 5.6.5p1, 2017.1.3.1f1