Reproduction steps:
1. Open the user's attached project
2. Drag shader from ExampleAssets/Shaders onto any of the cubes
3. Reset the cube's material to anything, that doesn't have that shader
4. Repeat steps 2 and 3 until Developer Tools Dialogue pops up
5. Press cancel repeatedly
Expected result: Editor throws an error
Actual result: Editor crashes
Reproducible with: 2020.3.19f1, 2021.1.21f1
Notes: I was able to reproduce it only a few times on 2021.1.21f1, however, there is another case with the same issue 1374208 on 2020.3