### 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)

valid = valid && test_conversion_with_regex("\"device\":-1,\"scancode\":65,\"physical_scancode\":66", "\"device\":-1,\"scancode\":65,\"physical_scancode\":66", &ProjectConverter3To4::rename_input_map_scancode, "custom rename", reg_container);
	valid = valid && test_conversion_with_regex("\"device\":0,\"button_index\":5,\"pressure\":0.0,\"pressed\":false,", "\"device\":0,\"button_index\":10,\"pressure\":0.0,\"pressed\":false,", &ProjectConverter3To4::rename_joypad_buttons_and_axes, "custom rename", reg_container);
	valid = valid && test_conversion_with_regex("\"device\":0,\"axis\":6,", "\"device\":0,\"axis\":4,", &ProjectConverter3To4::rename_joypad_buttons_and_axes, "custom rename", reg_container);
	valid = valid && test_conversion_with_regex("InputEventJoypadButton,\"button_index\":7,\"pressure\":0.0,\"pressed\":false,\"script\":null", "InputEventJoypadMotion,\"axis\":5,\"axis_value\":1.0,\"script\":null", &ProjectConverter3To4::rename_joypad_buttons_and_axes, "custom rename", reg_container);
	
	{
		String from = "instance";
		String to = "instantiate";
		String name = "AA.instance()";
		Vector<SourceLine> got = split_lines(name);
		String expected = "AA.instantiate()";
		custom_rename(got, from, to);
		String got_str = collect_string_from_vector(got);
		if (got_str != expected) {
			ERR_PRINT(vformat("Failed to convert custom rename \"%s\" to \"%s\", got \"%s\", instead.", name, expected, got_str));
		}
		valid = valid && (got_str == expected);
	}
	
	{
		{ String base = "var roman = kieliszek.";
	String expected = "kieliszek.";
	String got = get_object_of_execution(base);
	if (got != expected) {
		ERR_PRINT(vformat("Failed to get proper data from get_object_of_execution. \"%s\" should return \"%s\"(%d), got \"%s\"(%d), instead.", base, expected, expected.size(), got, got.size()));
	}
	valid = valid && (got == expected);
}
{
	String base = "r.";