### 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)

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) {
			for (unsigned int current_index = 0; RenamesMap3To4::class_renames[current_index][0]; current_index++) {
				if (line.contains(RenamesMap3To4::class_renames[current_index][0])) {
					bool found_ignored_items = false;
					// 
					if (line.contains(String(RenamesMap3To4::class_renames[current_index][0]) + ".")) {
						found_ignored_items = true;
						line = reg_container.class_tscn_regexes[current_index]->sub(line, "TEMP_RENAMED_CLASS.tscn", true);
						line = reg_container.class_gd_regexes[current_index]->sub(line, "TEMP_RENAMED_CLASS.gd", true);
						line = reg_container.class_shader_regexes[current_index]->sub(line, "TEMP_RENAMED_CLASS.shader", true);
					}
					// 
					line = reg_container.class_regexes[current_index]->sub(line, RenamesMap3To4::class_renames[current_index][1], true);
					// 
					if (found_ignored_items) {
						line = reg_container.class_temp_tscn.sub(line, reg_container.class_temp_tscn_renames[current_index], true);
						line = reg_container.class_temp_gd.sub(line, reg_container.class_temp_gd_renames[current_index], true);
						line = reg_container.class_temp_shader.sub(line, reg_container.class_temp_shader_renames[current_index], true);
					}
				}
			}
		}
	}
};
Vector<String> ProjectConverter3To4::check_for_rename_classes(Vector<String> &lines, const RegExContainer &reg_container) {