### Godot version

4.0 RC1

### System information

Linux Mint 20.3 Cinnamon

### Issue description

Tried converting a 3.5 game to 4.0 RC1. The conversion popup menu closed after a few seconds, and trying to edit the game crashes the entire engine with the following errors, which seem to be related to one music file not loading:
![errors](https://user-images.githubusercontent.com/125468288/219127087-f5a78035-4e4a-4625-aadb-e0cde6d5ac3d.png)

Not sure what's causing the issue, because when I created a new project with only that file and converted it I didn't get these errors, but consistently get them when trying to convert that game.

### Steps to reproduce

- Download the reproduction project below
- Import in Godot 4.0, and click "convert full project"
- If the bug happens, the engine will crash whenever trying to edit or run the converted project

### Minimal reproduction project

[Music Convertor Crash Demo.zip](https://github.com/godotengine/godot/files/10746591/Music.Convertor.Crash.Demo.zip)

RegEx keyword_gdscript_tool = RegEx("^tool");
	RegEx keyword_gdscript_export_single = RegEx("^export");
	RegEx keyword_gdscript_export_mutli = RegEx("([\t]+)export\\b");
	RegEx keyword_gdscript_onready = RegEx("^onready");
	RegEx keyword_gdscript_remote = RegEx("^remote func");
	RegEx keyword_gdscript_remotesync = RegEx("^remotesync func");
	RegEx keyword_gdscript_sync = RegEx("^sync func");
	RegEx keyword_gdscript_slave = RegEx("^slave func");
	RegEx keyword_gdscript_puppet = RegEx("^puppet func");
	RegEx keyword_gdscript_puppetsync = RegEx("^puppetsync func");
	RegEx keyword_gdscript_master = RegEx("^master func");
	RegEx keyword_gdscript_mastersync = RegEx("^mastersync func");
	RegEx gdscript_comment = RegEx("^\\s*#");
	RegEx csharp_comment = RegEx("^\\s*\\/\\/");
	
	RegEx keyword_csharp_remote = RegEx("\\[Remote(Attribute)?(\\(\\))?\\]");
	RegEx keyword_csharp_remotesync = RegEx("\\[(Remote)?Sync(Attribute)?(\\(\\))?\\]");
	RegEx keyword_csharp_puppet = RegEx("\\[(Puppet|Slave)(Attribute)?(\\(\\))?\\]");
	RegEx keyword_csharp_puppetsync = RegEx("\\[PuppetSync(Attribute)?(\\(\\))?\\]");
	RegEx keyword_csharp_master = RegEx("\\[Master(Attribute)?(\\(\\))?\\]");
	RegEx keyword_csharp_mastersync = RegEx("\\[MasterSync(Attribute)?(\\(\\))?\\]");
	
	LocalVector<RegEx *> color_regexes;
	LocalVector<String> color_renamed;
	
	LocalVector<RegEx *> class_tscn_regexes;
	LocalVector<RegEx *> class_gd_regexes;
	LocalVector<RegEx *> class_shader_regexes;