Bug 248164: REGRESSION(256867@main): caused crashes for several tests on debug bots, for instance <https://results.webkit.org/?suite=layout-tests&test=imported%2Fw3c%2Fweb-platform-tests%2Fcss%2Fcss-typed-om%2Fthe-stylepropertymap%2Finline%2Fset.tentative.html>