### 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 ((line.contains(".lock") || line.contains(".unlock")) && !line.contains("mtx") && !line.contains("mutex") && !line.contains("Mutex")) {
		line = reg_container.reg_image_lock.sub(line, "false # $1.lock() # TODOConverter40, Image no longer requires locking, `false` helps to not break one line if/else, so it can freely be removed", true);
		line = reg_container.reg_image_unlock.sub(line, "false # $1.unlock() # TODOConverter40, Image no longer requires locking, `false` helps to not break one line if/else, so it can freely be removed", true);
	}
	// 
	if (line.contains(".join")) {
		line = reg_container.reg_join.sub(line, "$2.join($1)", true);
	}
	// 
	if (line.contains("empty")) {
		line = reg_container.reg_is_empty.sub(line, "is_empty(", true);
	}
	// 
	if (line.contains("(") && line.contains(".")) {
		line = reg_container.reg_super.sub(line, "$1super.$2", true); // 
	}
	// 
	if (line.contains("parse")) {
		line = reg_container.reg_json_non_new.sub(line, "$1var test_json_conv = JSON.new()\n$1test_json_conv.parse($3\n$1$2test_json_conv.get_data()", true);
	}
	// 
	if (line.contains("to_json")) {