### Godot version

4.0 dev Beta 10

### System information

MacBook Pro M1 Max

### Issue description

After I imported font.ttf file and move it from one folder to another under ://res godot suddenly crashed, and it still crashes after restart.

### Steps to reproduce

Import some font.ttf file and try to move into different folder

### Minimal reproduction project

N/A
FontFallback *fd = font_owner.get_or_null(p_font_rid);
	ERR_FAIL_COND(!fd);
	Vector2i size = _get_size(fd, p_size);
	ERR_FAIL_COND(!_ensure_cache_for_size(fd, size));
	fd->cache[size]->descent = p_descent;
}
double TextServerFallback::_font_get_descent(const RID &p_font_rid, int64_t p_size) const {
	FontFallback *fd = font_owner.get_or_null(p_font_rid);
	ERR_FAIL_COND_V(!fd, 0.0);
	MutexLock lock(fd->mutex);
	Vector2i size = _get_size(fd, p_size);
	ERR_FAIL_COND_V(!_ensure_cache_for_size(fd, size), 0.0);
	if (fd->msdf) {
		return fd->cache[size]->descent * (double)p_size / (double)fd->msdf_source_size;
	} else {
		return fd->cache[size]->descent;
	}
}
void TextServerFallback::_font_set_underline_position(const RID &p_font_rid, int64_t p_size, double p_underline_position) {