Binding Nullable Bool to GridViewDataColumn

[Sharada]

Hi

I am binding bool datatype to a column in TreeListView
It shows checked Checkbox for TRUE and unchecked Checkbox for FALSE which is good.
But for NULL values it shows checkbox in disabled format.
I dont want to show checkbox for NULL values.
How can I achive this ? Please suggest.

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telerik:GridViewDataColumn DataMemberBinding="{Binding ManSprd}" Header="Man Sprd" IsVisible="{Binding Converter={StaticResource RelativeBlocksValueConverter2}, ConverterParameter=2}" />

I tried with  IsVisible property but it is also not giving desired output.