Should be fixed.

I'm using an inside code to use a CAS SSO authenticating system. There 
a stange difference in the way redirect.php behave between 4.0 and 4.1.
I believe there is a mistake:
  line 87:
     if (($imapuser !== null && ($imapuser == $_SESSION['imp']['user'])) &&
         ($pass !== null && ($pass == 
Secret::read(Secret::getKey('imp'), $_SESSION['imp']['pass'])))) {
  then FAILED

in the old code 4.O
     if ((is_null($imapuser) || ($imapuser == $_SESSION['imp']['user'])) &&
         (is_null($pass) || ($pass == 
Secret::read(Secret::getKey('imp'), $_SESSION['imp']['pass'])))) {
else FAILED

I don't understand.. I come with a CAS ticket using an horde auth, 
then sometimes, the imp session is already created via the side bar 
and you see a login failed in the imp framework..

Any ideas?. I'll patch to revert to get it working. I presume the else 
has gone somewhere else..