BUG: Exception with debug logs

When ui is set to 'Curses Blinkenlights' and debug logs are enabled,
we get an exception with 'embedded null character'.

Remove the NULL from the log, keeping the log message same as before.

Signed-off-by: Sudip Mukherjee <sudipm.mukherjee@gmail.com>

offlineimap/imapserver.py

@@ -215,8 +215,8 @@ class IMAPServer:
             authz = self.user_identity
 
         retval = NULL.join((authz, authc, passwd))
-        logsafe_retval = NULL.join((authz, authc, '(passwd hidden for log)'))
-        self.ui.debug('imap', '__plainhandler: returning %s' % logsafe_retval)
+        self.ui.debug('imap', '__plainhandler: returning %s %s '
+                      '(passwd hidden for log)' % (authz, authc))
         return retval
 
     def __xoauth2handler(self, response):