PHP Exception Leaks Encryption Key

infoleak.php

<?php
// Broken crypto code from https://github.com/slimphp/Slim/blob/develop/Slim/Crypt.php
function validateKeyLength($key, $module)
    {
        $keySize = strlen($key);
        $keySizeMin = 1;
        $keySizeMax = mcrypt_enc_get_key_size($module);
        $validKeySizes = mcrypt_enc_get_supported_key_sizes($module);
        if ($validKeySizes) {
            if (!in_array($keySize, $validKeySizes)) {
                throw new \InvalidArgumentException('Encryption key length must be one of: ' . implode(', ', $validKeySizes));
            }
        } else {
            if ($keySize < $keySizeMin || $keySize > $keySizeMax) {
                throw new \InvalidArgumentException(sprintf(
                    'Encryption key length must be between %s and %s, inclusive',
                    $keySizeMin,
                    $keySizeMax
                ));
            }
        }
    }

$module = mcrypt_module_open(MCRYPT_RIJNDAEL_128, '', MCRYPT_MODE_CBC, '');
validateKeyLength("HEY LOOK THIS IS THE SECRET KEY!!", $module);

/*
PHP Fatal error:  Uncaught exception 'InvalidArgumentException' with message 'Encryption key length must be one of: 16, 24, 32' in /tmp/test.php:10
Stack trace:
#0 /tmp/test.php(24): validateKeyLength('HEY LOOK THIS I...', Resource id #4)
                                        ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
#1 {main}
  thrown in /tmp/test.php on line 10

Fatal error: Uncaught exception 'InvalidArgumentException' with message 'Encryption key length must be one of: 16, 24, 32' in /tmp/test.php:10
Stack trace:
#0 /tmp/test.php(24): validateKeyLength('HEY LOOK THIS I...', Resource id #4)
#1 {main}
  thrown in /tmp/test.php on line 10
*/