Regression in "GDScript: fix segfault on invalid script" with const foo : GDScript= preload(...)

[lyuma]

#92035 causes a regression in projects which access inner classes from `const foo: GDScript = preload("./foo.gd"):

System info:
Godot v4.3.beta (8bf8f41) - Windows 10.0.19045 - Vulkan (Forward+) - dedicated NVIDIA GeForce RTX 3090 (NVIDIA; 31.0.15.3713) - Intel(R) Core(TM) i9-9900K CPU @ 3.60GHz (16 Threads)

MRP: GDScriptPreloadBug.zip

Steps to reproduce:

1. Open the project. There are errors.
2. Change test.gd from : GDScript = to := to infer type
3. Errors go away. Uncheck and check the plugin and it should print Hello World
4. Revert the change made in step 2.
5. There are still no errors?!?!?!

This issue does not reproduce when this PR is backed out. The MRP works fine in Godot 4.0.3 through May 17 bd2300d.

Originally posted by @lyuma in #92035 (comment)