QWidget::mapTo nullptr crash at win10 qt5.12.6

Qt5Widgets.dll!QWidget::mapTo(const QWidget * parent, const QPoint & pos) 行 4255 C++ 
Qt5Widgets.dll!QWidget::mapTo(const QWidget * parent, const QPoint & pos) 行 4255 C++ 
Qt5Widgets.dll!QWidgetBackingStore::qt_flush(QWidget * widget, const QRegion & region, QBackingStore * backingStore, QWidget * tlw, QPlatformTextureList * widgetTextures, QWidgetBackingStore * widgetBackingStore) 行 129 C++ 
Qt5Widgets.dll!QWidgetBackingStore::flush(QWidget * widget) 行 1470 C++
Qt5Widgets.dll!QWidgetBackingStore::endPaint(const QRegion &) 行 365 C++ 
Qt5Widgets.dll!QWidgetBackingStore::doSync() 行 1428 C++ 
Qt5Widgets.dll!QWidgetPrivate::syncBackingStore(const QRegion & region) 行 1960 C++ 
Qt5Widgets.dll!QWidgetWindow::handleExposeEvent(QExposeEvent * event) 行 996 C++ 
Qt5Widgets.dll!QWidgetWindow::event(QEvent * event) 行 337 C++ 
Qt5Widgets.dll!QApplicationPrivate::notify_helper(QObject * receiver, QEvent * e) 行 3702 C++>
Qt5Widgets.dll!QApplication::notify(QObject * receiver, QEvent * e) 行 3529 C+  geoscope.exe!main(int argc, char * * argv) 行 49 C+