QWidget::childAt returns empty children

#include <QApplication>
#include <QWidget>
#include <cassert>

int main(int argc, char **argv) {
  QApplication app(argc, argv);

  QWidget parent(nullptr, Qt::FramelessWindowHint);
  parent.resize(200, 200);

  QWidget *emptyChild = new QWidget(&parent);
  emptyChild->setGeometry(0, 100, 200, 0);

  assert(parent.childAt(100, 100) == nullptr);
}