diff --git a/EgtBEAMWALL.ViewerOptimizer/WarehouseWnd/WarehouseWndVM.vb b/EgtBEAMWALL.ViewerOptimizer/WarehouseWnd/WarehouseWndVM.vb
index 50aefac9..6363b262 100644
--- a/EgtBEAMWALL.ViewerOptimizer/WarehouseWnd/WarehouseWndVM.vb
+++ b/EgtBEAMWALL.ViewerOptimizer/WarehouseWnd/WarehouseWndVM.vb
@@ -660,7 +660,7 @@ Public Class WarehouseWndVM
                   Return
                End If
                For Each SPItem In SParamList
-                  If SParamList(ParamIndex - 1).dL <= 0 Then
+                  If IsNothing(SParamList(ParamIndex - 1).SectXMat) OrElse SParamList(ParamIndex - 1).dL <= 0 Then
                      MessageBox.Show(IncorrectValues_Msg, Error_Msg)
                      Return
                   End If
@@ -701,7 +701,7 @@ Public Class WarehouseWndVM
                   Return
                End If
                For Each SPItem In SParamList
-                  If SParamList(ParamIndex - 1).dW <= 0 OrElse SParamList(ParamIndex - 1).dL <= 0 Then
+                  If IsNothing(SParamList(ParamIndex - 1).SectXMat) OrElse SParamList(ParamIndex - 1).dW <= 0 OrElse SParamList(ParamIndex - 1).dL <= 0 Then
                      MessageBox.Show(IncorrectValues_Msg, Error_Msg)
                      Return
                   End If
@@ -1463,7 +1463,7 @@ Public Class SParam
 
    Public ReadOnly Property sMaterial As String
       Get
-         Return SectXMat.sMaterial(0)
+         Return If(IsNothing(SectXMat), "", SectXMat.sMaterial(0))
       End Get
    End Property