restored workaround for pre 4.3 php session restart issue

src/login.php

@@ -36,16 +36,15 @@ set_up_language($squirrelmail_language, TRUE, TRUE);
  * we get a new one.
  */
 sqsession_destroy();
-sqsession_is_active();
-$_SESSION=array();
-
-
 /**
  * PHP bug. http://bugs.php.net/11643 (warning, spammed bug tracker) and
  * http://bugs.php.net/13834
  * SID constant is not destroyed in PHP 4.1.2, 4.2.3 and maybe other
  * versions. Produces warning on login page. Bug should be fixed only in 4.3.0
  */
+@sqsession_is_active();
+$_SESSION=array();
+
 
 /**
  * This detects if the IMAP server has logins disabled, and if so,