### 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 reg = RegEx(String("\\b") + from + "\\b");
	CRASH_COND(!reg.is_valid());
	for (SourceLine &source_line : source_lines) {
		if (source_line.is_comment) {
			continue;
		}
		String &line = source_line.line;
		if (uint64_t(line.length()) <= maximum_line_length) {
			line = reg.sub(line, to, true);
		}
	}
};
Vector<String> ProjectConverter3To4::check_for_custom_rename(Vector<String> &lines, String from, String to) {
	Vector<String> found_renames;
	RegEx reg = RegEx(String("\\b") + from + "\\b");
	CRASH_COND(!reg.is_valid());
	int current_line = 1;
	for (String &line : lines) {
		if (uint64_t(line.length()) <= maximum_line_length) {
			TypedArray<RegExMatch> reg_match = reg.search_all(line);
			if (reg_match.size() > 0) {
				found_renames.append(line_formatter(current_line, from.replace("\\.", "."), to, line)); // 
			}
		}
		current_line++;
	}
	return found_renames;
}
void ProjectConverter3To4::rename_common(const char *array[][2], LocalVector<RegEx *> &cached_regexes, Vector<SourceLine> &source_lines) {