fix: authenticator crashing when session token invalid

server/authenticator.go

@@ -42,7 +42,7 @@ func (r *Authenticator) Authenticate(path string, exceptions []string) func(next
 				return err
 			}
 			session, error := r.userManager.GetSession(cookie.Value)
-			if error != nil {
+			if error != nil || session == nil {
 				SendError(401, context, fmt.Sprintf("session not found: %s", cookie.Value))
 				return fmt.Errorf("session not found: %s", cookie.Value)
 			}