Why does setTextColor() cause a segfault?

A line such as:

DICOM_Information__Patient_Information__Name->setTextColor(1,Qt::black);

where DICOM_Information__Patient_Information__Name is a
QTreeWidgetItem, should not cause a seg fault. Why does it do so then?I am quite sure that DICOM_Information__Patient_Information__Name is valid, so why does this happen?
:confused:

Maybe it's a null pointer after all? Or maybe a dangling pointer? Maybe you access it from non-GUI thread? Or it has only one column?