Reorganize wxDataViewMainWindow::ItemAdded() for better readability.

Reuse common code. No real changes.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@68792 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

src/generic/datavgen.cpp

@@ -1976,10 +1976,9 @@ bool wxDataViewMainWindow::ItemAdded(const wxDataViewItem & parent, const wxData
         wxDataViewVirtualListModel *list_model =
             (wxDataViewVirtualListModel*) GetOwner()->GetModel();
         m_count = list_model->GetCount();
-        UpdateDisplay();
-        return true;
     }
-
+    else
+    {
         SortPrepare();
 
         wxDataViewTreeNode * node;
@@ -2003,6 +2002,8 @@ bool wxDataViewMainWindow::ItemAdded(const wxDataViewItem & parent, const wxData
         node->ChangeSubTreeCount(1);
 
         m_count = -1;
+    }
+
     UpdateDisplay();
 
     return true;