[php-src] Issue #21068: finfo_open with directory cause invalid free

Issue: https://github.com/php/php-src/issues/21068
Author: ArchMaster2024

### Description

The following code:

```php

$magic_file = __DIR__ . DIRECTORY_SEPARATOR . 'magic私はガラスを食べられます';

$ret = @finfo_open(FILEINFO_NONE, $magic_file . ".non-exits私はガラスを食べられます");
var_dump($ret);

$dir = __DIR__ . "/bug61964-mb";
@mkdir($dir);

$magic_file_copy = $dir . "/magic私はガラスを食べられます.copy";
$magic_file_copy2 = $magic_file_copy . "2";
copy($magic_file, $magic_file_copy);
copy($magic_file, $magic_file_copy2);

$ret = finfo_open(FILEINFO_NONE, $dir);
var_dump($ret);

$ret = @finfo_open(FILEINFO_NONE, $dir);
var_dump($ret);

$ret = @finfo_open(FILEINFO_NONE, $dir. "/non-exits-dir私はガラスを食べられます");
var_dump($ret);

// write some test files to test folder
file_put_contents($dir . "/test1.txt", "string\n> Core\n> Me");
file_put_contents($dir . "/test2.txt", "a\nb\n");
@mkdir($dir . "/test-inner-folder私はガラスを食べられます");

finfo_open(FILEINFO_NONE, $dir);
echo "DONE: testing dir with files\n";

rmdir($dir . "/test-inner-folder私はガラスを食べられます");
unlink($dir . "/test1.txt");
unlink($dir . "/test2.txt");

unlink($magic_file_copy);
unlink($magic_file_copy2);
rmdir($dir);
<?php
```

Resulted in this output:
```
bool(false)

Warning: copy(/test_php/source/php/ext/fileinfo/tests/magic私はガラスを食べられます): Failed to open stream: No such file or directory in /test_php/source/php/ext/fileinfo/tests/bug61964-mb.php on line 13

Warning: copy(/test_php/source/php/ext/fileinfo/tests/magic私はガラスを食べられます): Failed to open stream: No such file or directory in /test_php/source/php/ext/fileinfo/tests/bug61964-mb.php on line 14
object(finfo)#1 (0) {
}
object(finfo)#2 (0) {
}
bool(false)

Notice: finfo_open(): Read of 8192 bytes failed with errno=21 Is a directory in /test_php/source/php/ext/fileinfo/tests/bug61964-mb.php on line 30

Warning: finfo_open(): offset `string' invalid in /test_php/source/php/ext/fileinfo/tests/bug61964-mb.php on line 30

Warning: finfo_open(): offset ` Core' invalid in /test_php/source/php/ext/fileinfo/tests/bug61964-mb.php on line 30

Warning: finfo_open(): offset ` Me' invalid in /test_php/source/php/ext/fileinfo/tests/bug61964-mb.php on line 30

Warning: finfo_open(): offset `a' invalid in /test_php/source/php/ext/fileinfo/tests/bug61964-mb.php on line 30

Warning: finfo_open(): offset `b' invalid in /test_php/source/php/ext/fileinfo/tests/bug61964-mb.php on line 30

Warning: finfo_open(): Failed to load magic database at "/test_php/source/php/ext/fileinfo/tests/bug61964-mb" in /test_php/source/php/ext/fileinfo/tests/bug61964-mb.php on line 30
DONE: testing dir with files

Warning: unlink(/test_php/source/php/ext/fileinfo/tests/bug61964-mb/magic私はガラスを食べられます.copy): No such file or directory in /test_php/source/php/ext/fileinfo/tests/bug61964-mb.php on line 37

Warning: unlink(/test_php/source/php/ext/fileinfo/tests/bug61964-mb/magic私はガラスを食べられます.copy2): No such file or directory in /test_php/source/php/ext/fileinfo/tests/bug61964-mb.php on line 38
```

But I expected this output instead:
```
bool(false)%A
object(finfo)#%d (0) {
}
object(finfo)#%d (0) {
}
bool(false)%A
Warning: finfo_open(): offset `string' invalid in %sbug61964-mb.php on line %d

Warning: finfo_open(): offset ` Core' invalid in %sbug61964-mb.php on line %d

Warning: finfo_open(): offset ` Me' invalid in %sbug61964-mb.php on line %d

Warning: finfo_open(): offset `a' invalid in %sbug61964-mb.php on line %d

Warning: finfo_open(): offset `b' invalid in %sbug61964-mb.php on line %d

Warning: finfo_open(): Failed to load magic database at "%sbug61964-mb" in %sbug61964-mb.php on line %d
DONE: testing dir with files
```


### PHP Version

```plain
PHP 8.4.17RC1 (cli) (built: Jan 25 2026 21:18:17) (NTS)
Copyright (c) The PHP Group
Zend Engine v4.4.17RC1, Copyright (c) Zend Technologies
```

### Operating System

Debian GNU/Linux 12 (bookworm) x86_64 (container run with podman)