### 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)

line = reg_container.reg_instantiate.sub(line, ".instantiate($1)", true);
	}
	// 
	if (contains_function_call(line, "move_and_slide(")) {
		int start = line.find("move_and_slide(");
		int end = get_end_parenthesis(line.substr(start)) + 1;
		if (end > -1) {
			String base_obj = get_object_of_execution(line.substr(0, start));
			String starting_space = get_starting_space(line);
			Vector<String> parts = parse_arguments(line.substr(start, end));
			if (parts.size() >= 1) {
				String line_new;
				// 
				line_new += starting_space + base_obj + "set_velocity(" + parts[0] + ")\n";
				// 
				if (parts.size() >= 2) {
					line_new += starting_space + base_obj + "set_(" + parts[1] + ")\n";
				}
				// 
				if (parts.size() >= 3) {
					line_new += starting_space + base_obj + "set_floor__enabled(" + parts[2] + ")\n";
				}
				// 
				if (parts.size() >= 4) {
					line_new += starting_space + base_obj + "set_(" + parts[3] + ")\n";
				}
				// 
				if (parts.size() >= 5) {
					line_new += starting_space + base_obj + "set_(" + parts[4] + ")\n";
				}