token session fix

php/AuthSCHClient.class.php

@@ -23,7 +23,9 @@ class AuthSCHClient {
                 
                 // get tokens from auth.sch.bme.hu
                 $this->authenticate();
-                //save tokendata to session
+                
+                //save tokendata to session (if we did authentication -> we have refresh token)
+                if(isset($this->tokens->refresh_token))
                     $_SESSION['tokens'] = serialize($this->tokens);
             } else {
                 // load tokendata from session