QStyleSheetStyle::pixelMetric using PM_TabBarBaseOverlap null ptr crash accessing w

qstylesheetstyle.cpp line 4713 attempts to use w->parentWidget() when w is null (which is its default value).

An example that is crashing for me is:

QQuickStyleItem::pixelMetric() [line 1072] calls QStyleSheetStyle::pixelMetric() with:
m = QStyle::PM_TabBarBaseOverlap
w = null (default param)