### 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);
	MutexLock lock(fd->mutex);
	Vector2i size = _get_size(fd, p_size);
	ERR_FAIL_COND(!_ensure_cache_for_size(fd, size));
	fd->cache[size]->kerning_map.clear();
}
void TextServerFallback::_font_remove_kerning(const RID &p_font_rid, int64_t p_size, const Vector2i &p_glyph_pair) {
	FontFallback *fd = font_owner.get_or_null(p_font_rid);
	ERR_FAIL_COND(!fd);
	MutexLock lock(fd->mutex);
	Vector2i size = _get_size(fd, p_size);
	ERR_FAIL_COND(!_ensure_cache_for_size(fd, size));
	fd->cache[size]->kerning_map.erase(p_glyph_pair);
}
void TextServerFallback::_font_set_kerning(const RID &p_font_rid, int64_t p_size, const Vector2i &p_glyph_pair, const Vector2 &p_kerning) {
	FontFallback *fd = font_owner.get_or_null(p_font_rid);
	ERR_FAIL_COND(!fd);
	MutexLock lock(fd->mutex);
	Vector2i size = _get_size(fd, p_size);
	ERR_FAIL_COND(!_ensure_cache_for_size(fd, size));
	fd->cache[size]->kerning_map[p_glyph_pair] = p_kerning;
}
Vector2 TextServerFallback::_font_get_kerning(const RID &p_font_rid, int64_t p_size, const Vector2i &p_glyph_pair) const {