Repro steps:

1. Install Unity 5.5.4p1 with the "Unity Editor Download Assistant" (Check "Microsoft Visual Studio Tools for Unity")
2. Create a new project
3. Uninstall "Microsoft Visual Studio Tools for Unity" while the Editor is still running
4. Select "Automatically close the application and attempt to restart them after the setup is complete"

Expected result: The Editor restarts
Actual result: The Editor crashes

Reproduced with: 5.5.4p1
Regression introduced in: 5.5.4p1
Did not reproduce on: 5.5.4f1, 5.5.3p4, 5.5.2p4, 5.4.5p4, 5.3.7p4