diff --git a/ProjectPage/OptionPanel/DrawOptionPanel/ManageLayerExpander/ManageLayerExpanderViewModel.vb b/ProjectPage/OptionPanel/DrawOptionPanel/ManageLayerExpander/ManageLayerExpanderViewModel.vb
index 9c9a648..ed3fb91 100644
--- a/ProjectPage/OptionPanel/DrawOptionPanel/ManageLayerExpander/ManageLayerExpanderViewModel.vb
+++ b/ProjectPage/OptionPanel/DrawOptionPanel/ManageLayerExpander/ManageLayerExpanderViewModel.vb
@@ -356,6 +356,7 @@ Namespace EgtCAM5
          ' determino Id di eventuale item sotto il mouse
          Dim nId As Integer = GDB_ID.NULL
          Dim TNode As LayerTreeViewItem = DirectCast(param, LayerTreeViewItem)
+         If isNothing(TNode) Then Return
          nId = TNode.Id
          ' se Id coincide con il corrente
          If nId <> GDB_ID.NULL And nId = m_nObjTreeOldId Then