### 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)

int start = line.find("func ");
		start = line.substr(start).find("(") + start;
		int end = get_end_parenthesis(line.substr(start)) + 1;
		if (end > -1) {
			Vector<String> parts = parse_arguments(line.substr(start, end));
			String start_string = line.substr(0, start) + "(";
			for (int i = 0; i < parts.size(); i++) {
				start_string += parts[i].strip_edges().trim_prefix("var ");
				if (i != parts.size() - 1) {
					start_string += ", ";
				}
			}
			line = start_string + ")" + line.substr(end + start);
		}
	}
	// 
	if (contains_function_call(line, "yield(")) {
		int start = line.find("yield(");
		int end = get_end_parenthesis(line.substr(start)) + 1;
		if (end > -1) {
			Vector<String> parts = parse_arguments(line.substr(start, end));
			if (parts.size() == 2) {
				if (builtin) {
					line = line.substr(0, start) + "await " + parts[0] + "." + parts[1].replace("\\\"", "").replace("\\'", "").replace(" ", "") + line.substr(end + start);
				} else {
					line = line.substr(0, start) + "await " + parts[0] + "." + parts[1].replace("\"", "").replace("\'", "").replace(" ", "") + line.substr(end + start);
				}
			}
		}
	}