Registering a callback on EditorApplication.Update that call AssetDatabase.StartAssetEditing() without calling AssetDatabase.StopAssetEditing() during the same callback will completely break the Unity Editor update cycles. EditorApplication.Update won't be fired anymore and the Editor will be in a corrupted state not responding to most inputs.

To reproduce:

1. Download attached project “Case1119972.zip" and open in Unity
2. Press Reproduction > Run Without Issue
3. Observe that in Console Unity prints thousands of Logs that it is Updating
4. Press Reproduction > Run Issue (will break the editor)

Expected results: Observe that in Console Unity still prints thousands of Logs that it is Updating
Actual results: Observe that EditorApplication.Update won't be fired anymore and the Editor will be in a corrupted state not responding to most Inputs

Notes:
- This issue appears on both Windows and macOS
- It would be great if a proper Error message informs the User that he's missing a call to AssetDatabase.StopAssetEditing() matching AssetDatabase.StartAssetEditing()
- Sometimes Console throws Native Error messages :

Assertion failed on expression: 'GetApplication().MayUpdate()'

(Filename: C:\buildslave\unity\build\Editor/Src/Application/PlayerLoopController.cpp Line: 166)

Refreshing native plugins compatible for Editor in 4.58 ms, found 5 plugins.
Preloading 2 native plugins for Editor in 0.16 ms.
Assertion failed on expression: '!performAutorepaint || GetApplication().MayUpdate()'

(Filename: C:\buildslave\unity\build\Editor/Platform/Windows/EditorWindows.cpp Line: 2799)

Reproduced on 2017.4.0f1, 2017.4.19f1, 2018.2.20f1, 2018.3.3f1, 2019.1.0b1 and 2019.2.0a3