message: Ensure RDHeaderView remains valid when deferring work
diff: #include <QMouseEvent>
  #include <QPainter>
  #include <QPixmap>
  +#include <QPointer>
  #include "Code/QRDUtils.h"
  /////////////////////////////////////////////////////////////////////////////////
  @@ -476,9 +477,13 @@ void RDHeaderView::setRootIndex(const QModelIndex &index)
  // *before* the root index changes).
  if(!m_sectionStretchHints.isEmpty())
  {
  - GUIInvoke::defer([this]() {
  - cacheSectionMinSizes();
  - resizeSectionsWithHints();
  + QPointer<RDHeaderView> ptr;
  + GUIInvoke::defer([ptr]() {
  + if(ptr)
  + {
  + ptr->cacheSectionMinSizes();
  + ptr->resizeSectionsWithHints();
  + }
  });
  }
  }
  