### 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)

if (parts.size() == 2) {
				line = line.substr(0, start) + "tween_callback(Callable(" + parts[0] + ", " + parts[1] + "))" + line.substr(end + start);
			} else if (parts.size() >= 3) {
				line = line.substr(0, start) + "tween_callback(Callable(" + parts[0] + ", " + parts[1] + ").bind(" + connect_arguments(parts, 2).substr(1).lstrip(" [").rstrip("] ") + "))" + line.substr(end + start);
			}
		}
	}
	// 
	// 
	if (contains_function_call(line, "start(")) {
		int start = line.find("start(");
		int end = get_end_parenthesis(line.substr(start)) + 1;
		// 
		if (!line.begins_with("func ")) {
			if (end > -1) {
				Vector<String> parts = parse_arguments(line.substr(start, end));
				if (parts.size() == 2) {
					line = line.substr(0, start) + "start(Callable(" + parts[0] + ", " + parts[1] + "))" + line.substr(end + start);
				} else if (parts.size() >= 3) {
					line = line.substr(0, start) + "start(Callable(" + parts[0] + ", " + parts[1] + ").bind(" + parts[2] + ")" + connect_arguments(parts, 3) + ")" + line.substr(end + start);
				}
			}
		}
	}
	// 
	if (line.contains(" _init(") && line.rfind(":") > 0) {
		//     
		// 
		int indent = line.count("\t", 0, line.find("func"));
		int super_start = line.find(".(");