### 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_V(!fd, 0);
	MutexLock lock(fd->mutex);
	Vector2i size = _get_size_outline(fd, p_size);
	ERR_FAIL_COND_V(!_ensure_cache_for_size(fd, size), 0);
	return fd->cache[size]->textures.size();
}
void TextServerFallback::_font_clear_textures(const RID &p_font_rid, const Vector2i &p_size) {
	FontFallback *fd = font_owner.get_or_null(p_font_rid);
	ERR_FAIL_COND(!fd);
	MutexLock lock(fd->mutex);
	Vector2i size = _get_size_outline(fd, p_size);
	ERR_FAIL_COND(!_ensure_cache_for_size(fd, size));
	fd->cache[size]->textures.clear();
}
void TextServerFallback::_font_remove_texture(const RID &p_font_rid, const Vector2i &p_size, int64_t p_texture_index) {
	FontFallback *fd = font_owner.get_or_null(p_font_rid);
	ERR_FAIL_COND(!fd);
	MutexLock lock(fd->mutex);
	Vector2i size = _get_size_outline(fd, p_size);
	ERR_FAIL_COND(!_ensure_cache_for_size(fd, size));
	ERR_FAIL_INDEX(p_texture_index, fd->cache[size]->textures.size());
	fd->cache[size]->textures.remove_at(p_texture_index);
}
void TextServerFallback::_font_set_texture_image(const RID &p_font_rid, const Vector2i &p_size, int64_t p_texture_index, const Ref<Image> &p_image) {