Remove superfluous log message

If we reach this point, we're likely already logging the error somewhere else (i.e. the session handler in use), so there's no point on logging the exception's message again.

lib/SimpleSAML/Logger.php

@@ -316,7 +316,6 @@ class Logger
                 $s = Session::getSessionFromRequest();
             } catch (\Exception $e) {
                 // loading session failed. We don't care why, at this point we have a transient session, so we use that
-                self::error('Cannot load or create session: '.$e->getMessage());
                 $s = Session::getSessionFromRequest();
             }
             self::$trackid = $s->getTrackID();