If you right click at the top of the Inspector window of a preset and select Reset, it will remove the preset type from the preset rendering it useless. You should not be able to reset a preset.

1. Open Unity
2. Open the attached project
3. Find RigidBody2D.preset in the project view and select it
4. In the Inspector, right click by the preset name and select Reset

Expected Result:
You should not be able to reset the preset.

Actual Result:
The preset is reset and the type is removed. The preset can no longer be used and must be deleted.

Tested on Windows.

Occurs on 2018.3.12, 2019.1.0a1, 2019.2.0a1, 2019.3.0a1