To reproduce:
1. Open attached project
2. Select "spritebug.jpg"
3. In the Inspector press Sprite Editor
4. In the Sprite Editor make a rectangle
5. There should be a pop up in the bottom right corner
6. Change Positive Width or Height value to negative
7. Create a new rectangle and try to select the rectangle with the negative value

Expected result: the drawn rectangle is editable and can be deleted
Actual result: you can't select or delete the rectangle with negative Position Width or Height value

Reproduced on:
2017.4.0f1 2017.4.13f1 2018.2.13f1 2018.3.0b6 2019.1.0a5

Notes:
Unity crashed when changes were applied.
After re-opening Unity, the sprite is corrupted and getting NullRefferenceExceptions in the console.