When printing with custom PageSizes, my application asserts.

ASSERT failure in QList<T>::at: "index out of range", file ../../include/QtCore/../../src/corelib/tools/qlist.h, line 472

Digging through the code i found in:
void QWin32PrintEnginePrivate::updateCustomPaperSize() on
qtbase\src\printsupport\kernel\qprintengine_win.cpp:1966

this: paper_size = paperSizes.at(paperSize).first;

shouldn't paperSize be i?

Attached is a patch that seems to fix the issue.