LookupGrid: Prevent crash when selectedvalues contains dbnull

Controls.LookupGrid/frmLookupGrid.vb

@@ -70,6 +70,8 @@ Public Class frmLookupGrid
 
         If SelectedValues Is Nothing Then
             SelectedValues = New List(Of String)
+        Else
+            SelectedValues = SelectedValues.Where(Function(v) Not (IsDBNull(v) OrElse String.IsNullOrWhiteSpace(v))).ToList()
         End If
 
         ' Bereits ausgewählte Werte im grid auswählen
@@ -131,6 +133,7 @@ Public Class frmLookupGrid
                     Dim row As DataRow = rowView.Row
                     Dim value = row.Item(_DataColumn)
 
+                    If Not (IsDBNull(value) OrElse String.IsNullOrWhiteSpace(value)) Then
                         If SelectedValues.Contains(value) Then
                             If MultiSelect Then
                                 row.Item(0) = True
@@ -139,6 +142,9 @@ Public Class frmLookupGrid
                             End If
                         End If
                     End If
+                End If
+
+
             Next
         End If
     End Sub