### 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)

int end = line.size() - 1; // 
	int variable_start = end - 1;
	int start = end - 1;
	bool is_possibly_nodepath = false;
	bool is_valid_nodepath = false;
	while (start >= 0) {
		char32_t character = line[start];
		bool is_variable_char = (character >= 'A' && character <= 'Z') || (character >= 'a' && character <= 'z') || character == '.' || character == '_';
		bool is_nodepath_start = character == '$';
		bool is_nodepath_sep = character == '/';
		if (is_variable_char || is_nodepath_start || is_nodepath_sep) {
			if (start == 0) {
				break;
			} else if (is_nodepath_sep) {
				// 
				is_possibly_nodepath = true;
			} else if (is_nodepath_start) {
				// 
				is_valid_nodepath = true;
				break;
			}
			if (!is_possibly_nodepath) {
				variable_start--;