How to reproduce:
1. Download the attached project, extract it and clear its Library folder
2. Open the project
3. Inspect "Test Shader.shader" and press "Show compiled code" in its Inspector
4. Observe the console

Expected result: Shader compiler does not crash
Actual result: Shader compiler crashes when trying to disassemble previously uncompiled, broken shader

Reproduced in: 2020.2.0a13, 2020.1.0b10, 2020.1.0a16
Not reproducible: 2020.1.0a15, 2019.3.15f1, 2018.4.23f1 (Can't reproduce it here because the Editor tries and fails to compile the shader every time even after clearing the Library)

Note: This only reproduces with shaders that haven't been compiled before - in other words, the Editor does not know that they're broken. Since in the "Not reproducible" versions the Editor already knows that the shader is broken the shader compiler crash does not reproduce.