jj: handle dragdrop when row is nothing

app/DD_PM_WINDREAM/ClassDragDrop.vb

@@ -57,6 +57,7 @@ Public Class ClassDragDrop
                     Dim row As DataRow = view.GetDataRow(downHitInfo.RowHandle)
                     Dim source As String = view.GridControl.Name
 
+                    If Not IsNothing(row) Then
                         dragDropData = row.Item("GUID") & "|" & source
 
                         view.GridControl.DoDragDrop(dragDropData, DragDropEffects.Move)
@@ -65,6 +66,7 @@ Public Class ClassDragDrop
                         DevExpress.Utils.DXMouseEventArgs.GetMouseArgs(e).Handled = True
                     End If
                 End If
+            End If
         Catch ex As Exception
             MsgBox("Error in view_MouseMove: " & ex.Message, MsgBoxStyle.Critical)
         End Try