UI: Remove redundant view reference in view items

The new view item base class already holds a reference to the view, no
need to have one in the derived class as well.

source/blender/editors/include/UI_grid_view.hh

@@ -36,8 +36,6 @@ class AbstractGridViewItem : public AbstractViewItem {
   friend class AbstractGridView;
   friend class GridViewLayoutBuilder;
 
-  const AbstractGridView *view_;
-
  protected:
   /** Reference to a string that uniquely identifies this item in the view. */
   StringRef identifier_{};

source/blender/editors/interface/views/grid_view.cc

@@ -29,8 +29,6 @@ AbstractGridViewItem &AbstractGridView::add_item(std::unique_ptr<AbstractGridVie
   items_.append(std::move(item));
 
   AbstractGridViewItem &added_item = *items_.last();
-  added_item.view_ = this;
-
   item_map_.add(added_item.identifier_, &added_item);
   register_item(added_item);
 
@@ -181,7 +179,7 @@ const AbstractGridView &AbstractGridViewItem::get_view() const
     throw std::runtime_error(
         "Invalid state, item must be added through AbstractGridView::add_item()");
   }
-  return *view_;
+  return dynamic_cast<AbstractGridView &>(*view_);
 }
 
 /* ---------------------------------------------------------------------- */