Show wxPGProperty editor dialog only in response to clicking main editor button

Properties with editor dialog (like those derived from wxEditorDialogProperty) should show it only in response to clicking the main editor button.

src/propgrid/propgrid.cpp

@@ -3586,7 +3586,7 @@ bool wxPropertyGrid::HandleCustomEditorEvent( wxEvent &event )
 
     //
     // Try common button handling
-    if ( m_wndEditor2 && event.GetEventType() == wxEVT_BUTTON )
+    if ( IsMainButtonEvent(event) )
     {
         wxPGEditorDialogAdapter* adapter = selected->GetEditorDialog();