When hiding header for QTreeWidget I get this:
QAccessibleTree::indexFromLogical: invalid index: 1 0 for QTreeWidget(0xf94748, name = "treeWidget")
Cannot creat accessible child interface for object: QTreeWidget(0xf94748, name = "treeWidget") index: 1

Attached the minimal app with the issue.(NOTE: delete untitled.pro.user in order to configure build paths for the app)
These two lines are enough to reproduce it:
ui->treeWidget->setHeaderHidden(true);
ui->treeWidget->addTopLevelItem(new QTreeWidgetItem((QTreeWidget*)NULL, QStringList() << "Hello bugs"));