Disconnect item model before deleting RDTreeWidget/RDTreeView

* This avoids odd races where some events might be fired mid-destruction and
  encounter the item model in an undefined state.

qrenderdoc/Widgets/Extended/RDTreeView.cpp

@@ -131,6 +131,8 @@ RDTreeView::RDTreeView(QWidget *parent) : QTreeView(parent)
 
 RDTreeView::~RDTreeView()
 {
+  setModel(NULL);
+
   delete m_ElidedTooltip;
 }
 

qrenderdoc/Widgets/Extended/RDTreeWidget.cpp

@@ -596,6 +596,8 @@ RDTreeWidget::RDTreeWidget(QWidget *parent) : RDTreeView(parent)
 
 RDTreeWidget::~RDTreeWidget()
 {
+  RDTreeView::setModel(NULL);
+
   delete m_root;
   delete m_model;
 }