Fix E_DEPRECATED warning when using Auth_SASL::factory() (#5401)

CHANGELOG

@@ -10,6 +10,7 @@ CHANGELOG Roundcube Webmail
 - Fix bug where memcache_debug didn't work for session operations
 - Fix bug where Message-ID domain part was tied to username instead of current identity (#5385)
 - Fix bug where blocked.gif couldn't be attached to reply/forward with insecure content
+- Fix E_DEPRECATED warning when using Auth_SASL::factory() (#5401)
 
 RELEASE 1.2.1
 -------------

program/lib/Roundcube/rcube_imap_generic.php

@@ -575,7 +575,8 @@ class rcube_imap_generic
                     $user  = '';
                 }
 
-                $auth_sasl = Auth_SASL::factory('digestmd5');
+                $auth_sasl = new Auth_SASL;
+                $auth_sasl = $auth_sasl->factory('digestmd5');
                 $reply     = base64_encode($auth_sasl->getResponse($authc, $pass,
                     base64_decode($challenge), $this->host, 'imap', $user));