How to reproduce:
1. Open attached project "case_1119351-Panmateria_Project_Stripped" and scene "Biome01_Sector01"
2. Select "ProblemObject" in the Hierarchy Window
3. Click "Biome01_Sector01_material" in the GameObject's Mesh Renderer's Materials list in the Inspector to highlight the material in the Project Window
4. While the Material is highlighted quickly press the "Generate Mask Texture" button under the Map Generator script Component

Expected result: the command successfully generates the texture
Actual result: Unity crashes

Reproducible with: 2017.4.19f1, 2018.3.3f1, 2019.1.0b1, 2019.2.0a3

Note: the Project Window must be open for the Material to be highlightable and the problem to reproduce