fix for assert failure when first paint event occurs before first idle event, #10085

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@56474 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

src/generic/treectlg.cpp

@@ -2461,6 +2461,7 @@ int wxGenericTreeCtrl::GetLineHeight(wxGenericTreeItem *item) const
 void wxGenericTreeCtrl::PaintItem(wxGenericTreeItem *item, wxDC& dc)
 {
     item->SetFont(this, dc);
+    item->CalculateSize(this, dc);
 
     wxCoord text_h = item->GetTextHeight();