Comment 7 for bug 1577277

Something strange is happening with VerticalView of poppler-qml-plugin. When destroying the page displaying the PDF, the VerticalView in QML reports that it is being destroyed (I added Component.onDestruction: print("destroying VerticalView"), but it is not yet being fully destroyed, and in C++ when calling .isNull() on the VerticalView, it appears to return false.

In ucheader.cpp we detect a change in the header visibility (it is made invisible because it is also being destroyed) which triggers an update in the flickable margins. We always first check there that the flickable is still valide using m_flickable.isNull(), which reports that the flickable is still valid. However, when calling functions on m_flickable, we get a segfault.

This is weird and requires further investigation. But I will attach a branch with a workaround for the document viewer.