Print to pdf crashes or gives error message to console

My software meets this bug: https://lalescu.ro/liviu/fet/

Partially reproducible with /Qt/Examples/Qt-6.0.0/widgets/itemviews/spreadsheet

If I try to print to pdf file from this Qt example I get on GNU/Linux openSUSE Tumbleweed this warning on the command line: "QPageRanges::addRange: 'from' and 'to' must be greater than 0"

If I try to print to pdf from my application on GNU/Linux openSUSE Tumbleweed, I get this warning and also the pdf does not contain the correct data, only empty tables (it should be a filled HTML table).

If a user tries to print to pdf from Mac OS X 10.15.6, he gets a crash (https://lalescu.ro/liviu/fet/forum/index.php?topic=4764.0 is the link to my software forum's post).