Only remove E_WARNING from error level

Author: fritzmg

src/Symfony/Component/HttpKernel/Kernel.php

@@ -407,7 +407,8 @@ protected function initializeContainer()
         $cachePath = $cache->getPath();
 
         // Silence E_WARNING to ignore "include" failures - don't use "@" to prevent silencing fatal errors
-        $errorLevel = error_reporting(\E_ALL ^ \E_WARNING);
+        $errorLevel = error_reporting();
+        error_reporting($errorLevel & ~\E_WARNING);
 
         try {
             if (is_file($cachePath) && \is_object($this->container = include $cachePath)