### 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)

Vector<SourceLine> got = split_lines(name);
	(this->*func)(got, reg_container, builtin_script);
	String got_str = collect_string_from_vector(got);
	ERR_FAIL_COND_V_MSG(expected != got_str, false, vformat("Failed to convert %s \"%s\" to \"%s\", got instead \"%s\"", what, name, expected, got_str));
	return true;
}
bool ProjectConverter3To4::test_conversion_with_regex(String name, String expected, void (ProjectConverter3To4::*func)(Vector<SourceLine> &, const RegExContainer &), String what, const RegExContainer &reg_container) {
	Vector<SourceLine> got = split_lines(name);
	(this->*func)(got, reg_container);
	String got_str = collect_string_from_vector(got);
	ERR_FAIL_COND_V_MSG(expected != got_str, false, vformat("Failed to convert %s \"%s\" to \"%s\", got instead \"%s\"", what, name, expected, got_str));
	return true;
}
bool ProjectConverter3To4::test_conversion_basic(String name, String expected, const char *array[][2], LocalVector<RegEx *> &regex_cache, String what) {
	Vector<SourceLine> got = split_lines(name);
	rename_common(array, regex_cache, got);
	String got_str = collect_string_from_vector(got);
	ERR_FAIL_COND_V_MSG(expected != got_str, false, vformat("Failed to convert %s \"%s\" to \"%s\", got instead \"%s\"", what, name, expected, got_str));
	return true;
}
bool ProjectConverter3To4::test_conversion(RegExContainer &reg_container) {