### 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)

parts.append(line.substr(start_part + 1, current_index - start_part - 1));
					start_part = current_index;
				}
				break;
			};
			case '[': {
				parts_counter++;
				if (parts_counter == 1 && !is_inside_string) {
					start_part = current_index;
				}
				break;
			};
			case ']': {
				parts_counter--;
				if (parts_counter == 0 && !is_inside_string) {
					parts.append(line.substr(start_part, current_index - start_part));
					start_part = current_index;
				}
				break;
			};
			case ',': {
				if (parts_counter == 1 && !is_inside_string) {
					parts.append(line.substr(start_part + 1, current_index - start_part - 1));
					start_part = current_index;
				}
				break;
			};
			case '"': {
				if (previous_character != '\\')
					is_inside_string = !is_inside_string;