Fix bug in crsf token handling

phpcs-errors:238 phpunit-status:successful

upload.php

@@ -6,6 +6,10 @@
 $target .= basename($_FILES['uploaded']['name']);
 $targetpart = basename($_FILES['uploaded']['name']);
 
+if (session_status() != PHP_SESSION_ACTIVE) {
+    session_start();
+}
+
 if (validateAntiCsrfToken() === false) {
     throw new WrongCsrfTokenException();
 }