str_getcsv ending with escape zero segfualt

### Description

This was reported by @dstogov in https://github.com/php/php-src/commit/aff46d75e12659b9babc8aa4a74e820f5f29bd68#commitcomment-126371916

```php
<?php
str_getcsv("y","","y","\000");
```

results in segfault


### PHP Version

PHP 8.3.0RC1

### Operating System

_No response_