Found in logs:
[error] 3324612#3324612: *97174 FastCGI sent in stderr: "PHP message: PHP Fatal error: Uncaught TypeError: Tracker_FormElementFactory::getUsedListFieldById(): Argument #2 ($field_id) must be of type int, null given, called in /usr/share/tuleap/plugins/graphontrackersv5/include/DataTransformation/GraphOnTrackersV5_Chart_PieDataBuilder.php on line 42 and defined in /usr/share/tuleap/plugins/tracker/include/Tracker/FormElement/Tracker_FormElementFactory.php:843