nodeview: clear edges first

app/widget/nodeview/nodeviewcontext.cpp

@@ -44,6 +44,13 @@ NodeViewContext::NodeViewContext(Node *context, QGraphicsItem *item) :
   connect(context_, &Node::NodeRemovedFromContext, this, &NodeViewContext::RemoveChild, Qt::DirectConnection);
 }
 
+NodeViewContext::~NodeViewContext()
+{
+  // Delete edges before items, because the edge constructor references the items
+  qDeleteAll(edges_);
+  edges_.clear();
+}
+
 void NodeViewContext::AddChild(Node *node)
 {
   if (!context_) {

app/widget/nodeview/nodeviewcontext.h

@@ -17,6 +17,8 @@ class NodeViewContext : public QObject, public QGraphicsRectItem
 public:
   NodeViewContext(Node *context, QGraphicsItem *item = nullptr);
 
+  virtual ~NodeViewContext() override;
+
   Node *GetContext() const
   {
     return context_;