Fix strtolower() deprecation when invoked with NULL

Author: thePanz

lib/classes/Swift/Transport/Esmtp/AuthHandler.php

@@ -39,7 +39,7 @@ class Swift_Transport_Esmtp_AuthHandler implements Swift_Transport_EsmtpHandler
     /**
      * The auth mode for authentication.
      *
-     * @var string
+     * @var string|null
      */
     private $_auth_mode;
 
@@ -248,7 +248,7 @@ public function resetState()
      */
     protected function _getAuthenticatorsForAgent()
     {
-        if (!$mode = strtolower($this->_auth_mode)) {
+        if (!$this->_auth_mode || !$mode = strtolower($this->_auth_mode)) {
             return $this->_authenticators;
         }
 

lib/classes/Swift/Transport/EsmtpTransport.php

@@ -134,18 +134,18 @@ public function getTimeout()
     /**
      * Set the encryption type (tls or ssl).
      *
-     * @param string $encryption
+     * @param string|null $encryption
      *
      * @return $this
      */
     public function setEncryption($encryption)
     {
-        $encryption = strtolower($encryption);
-        if ('tls' == $encryption) {
+        $normalizedEncryption = $encryption ? strtolower($encryption) : '';
+        if ('tls' === $normalizedEncryption) {
             $this->_params['protocol'] = 'tcp';
             $this->_params['tls'] = true;
         } else {
-            $this->_params['protocol'] = $encryption;
+            $this->_params['protocol'] = $normalizedEncryption;
             $this->_params['tls'] = false;
         }