Declaring an inner class that extends a variable name crashes the engine, instead of just reporting an error (GDScript)

[nenad-jalsovec]

Godot version

4.0 stable official

System information

Windows 10

Issue description

This has been posted by an user over at godotforums.org, in a more complicated form. I just made a super-minimal example that's trivial to reproduce. Don't know if this was already reported.

Engine crashes to desktop without a warning when following script is created and then saved:

var B = 1
class A extends B:
	pass

I also tried it in console version with verbose and debug flags enabled. The output to console was:
ERROR: FATAL: Condition "!exists" is true.
at: operator[] (./core/templates/hash_map.h:504)

Steps to reproduce

1. Create a new GDScript script file
2. Enter the following code

var B = 1
class A extends B:
	pass

3. Save the script file.
4. Engine crashes immediately upon save.

Minimal reproduction project

N/A, trivial to reproduce.