### 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)

maximum_file_size = p_maximum_file_size_kb * 1024;
	maximum_line_length = p_maximum_line_length;
}
bool ProjectConverter3To4::convert() {
	print_line("Starting conversion.");
	uint64_t conversion_start_time = Time::get_singleton()->get_ticks_msec();
	RegExContainer reg_container = RegExContainer();
	int cached_maximum_line_length = maximum_line_length;
	maximum_line_length = 10000; 
	ERR_FAIL_COND_V_MSG(!test_array_names(), false, "Cannot start converting due to problems with data in arrays.");
	ERR_FAIL_COND_V_MSG(!test_conversion(reg_container), false, "Aborting conversion due to validation tests failing");
	maximum_line_length = cached_maximum_line_length;
	
	
	{
		String converter_text = "; Project was converted by built-in tool to Godot 4.0";