### 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_json_to.sub(line, "JSON.new().stringify", true);
	}
	// 
	if (line.contains("parse_json")) {
		line = reg_container.reg_json_parse.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("JSON.print(")) {
		line = reg_container.reg_json_print.sub(line, "JSON.stringify(", true);
	}
	// 
	if (line.contains("get_node")) {
		line = line.replace("get_node(@", "get_node(");
	}
	if (line.contains("export")) {
		// 
		line = reg_container.reg_export_typed.sub(line, "export var $2: $1");
		// 
		line = reg_container.reg_export_inferred_type.sub(line, "export var $1 :=");
		// 
		line = reg_container.reg_export_simple.sub(line, "export var $2: $1");
		// 
		line = reg_container.reg_export_advanced.sub(line, "export var $2$3 # ($1)");
	}
	// 
	if (line.contains("setget")) {
		line = reg_container.reg_setget_setget.sub(line, "var $1$2: get = $4, set = $3", true);
	}
	// 
	if (line.contains("setget")) {