Fix coding style missed by phpbcf (#2901)

$ composer require --dev friendsofphp/php-cs-fixer

$ echo >.php-cs-fixer.dist.php "<?php

$finder = PhpCsFixer\Finder::create()
    ->in(__DIR__);

$rules = [
    '@PSR12' => true,
    // '@PSR12:risky' => true,
    '@PHP74Migration' => true,
    // '@PHP74Migration:risky' => true,
    // buggy, duplicates existing comment sometimes
    'no_break_comment' => false,
    'array_syntax' => true,
    'lowercase_static_reference' => true,
    'visibility_required' => false,
    // Too much noise
    'binary_operator_spaces' => false,
    'heredoc_indentation' => false,
    'trailing_comma_in_multiline' => false,
];

$config = new PhpCsFixer\Config();

return $config
    ->setRules($rules)
    // ->setRiskyAllowed(true)
    ->setFinder($finder);

"

$ vendor/bin/php-cs-fixer --version
PHP CS Fixer 3.8.0 BerSzcz against war! by Fabien Potencier and Dariusz Ruminski.
PHP runtime: 8.1.7

$ vendor/bin/php-cs-fixer fix
$ rm .php-cs-fixer.cache
$ vendor/bin/php-cs-fixer fix

lib/Debug.php

@@ -114,7 +114,7 @@ class Debug
         $calling = end($backtrace);
         $message = $calling['file'] . ':'
             . $calling['line'] . ' class '
-            . (isset($calling['class']) ? $calling['class'] : '<no-class>') . '->'
+            . ($calling['class'] ?? '<no-class>') . '->'
             . $calling['function'] . ' - '
             . $text;