I have error message (Failed Ajax request or invalid JSON returned.) when trying add new Submission Preparation Checklist or edit.
Error logs show [17-Feb-2021 13:41:23 Europe/Warsaw] PHP Warning: Declaration of SubmissionChecklistForm::initData($args) should be compatible with Form::initData() in /OJS_backup/lib/pkp/controllers/grid/settings/submissionChecklist/form/SubmissionChecklistForm.inc.php on line 19
[17-Feb-2021 13:41:23 Europe/Warsaw] PHP Warning: Cannot modify header information - headers already sent by (output started at /OJS_backup/lib/pkp/controllers/grid/settings/submissionChecklist/form/SubmissionChecklistForm.inc.php:19) in /OJS_backup/lib/pkp/classes/core/PKPRouter.inc.php on line 408
Haw fix it?