PSR12.Files.FileHeader false positive when file only contains docblock

```
FOUND 1 ERROR AFFECTING 1 LINE
---------------------------------------------------------------------------------------------------------------------
 5 | ERROR | [x] Header blocks must be followed by a single blank line
```
is unfixable.
It doesn't respect a file that only contains a docblock.

code is:
```php
<?php

/**
 * Here go your local configs
 */
```