[HttpKernel] fixed an error message

Author: fabpot

DataCollector/RequestDataCollector.php

@@ -298,10 +298,11 @@ private function getCookieHeader($name, $value, $expires, $path, $domain, $secur
             } elseif ($expires instanceof \DateTime) {
                 $expires = $expires->getTimestamp();
             } else {
-                $expires = strtotime($expires);
-                if (false === $expires || -1 == $expires) {
-                    throw new \InvalidArgumentException(sprintf('The "expires" cookie parameter is not valid.', $expires));
+                $tmp = strtotime($expires);
+                if (false === $tmp || -1 == $tmp) {
+                    throw new \InvalidArgumentException(sprintf('The "expires" cookie parameter is not valid (%s).', $expires));
                 }
+                $expires = $tmp;
             }
 
             $cookie .= '; expires='.str_replace('+0000', '', \DateTime::createFromFormat('U', $expires, new \DateTimeZone('GMT'))->format('D, d-M-Y H:i:s T'));