Editor crashes while processing class when extern method doesn't have DllImport attribute

Steps to reproduce:

1. Open attached project
2. Open Code Coverage window
3. Start and stop recording

• Editor crashes

Note: Add missing [DllImport] attribute to fix this crash, or try adding [ExcludeFromCoverage] on the last class that was being processed by code coverage package when the crash happened (you can find class name in Editor.log)

Reproduced with: 2019.4.8f1, 2021.2.0a19
Package: 1.0.0, 1.1.0