Radio button list databind problem for null values

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Hey guys, I have this problem from few weeks. I have a form with radio button list 1.Active 2.Inactive as list items .
In another page I have dataformview to search and edit above filled data. If user did not select any option from the radiobutton list during submission and tries to edit null data in form view it throws an error saying "RadioButtonList' has a SelectedValue which is invalid because it does not exist in the list of items" .How should I approach for this problem. I am using varchar as datatype for radiobutton. Also which datatype would be best for radiobutton (to save data and bind).Do I need to set default value for radiobutton list? Please help me. Appreciate your response.
Here is the sample code of radiobutton submission

<asp:RadioButtonList ID="RadioButtonList1" runat="server" AutoPostBack="True"
                   onselectedindexchanged="RadioButtonList1_SelectedIndexChanged"
                   style="text-align: left; font-size: medium;" RepeatDirection="Horizontal"
                   RepeatLayout="Flow" AppendDataBoundItems="True">
                   <asp:ListItem Text="Active">Active</asp:ListItem>
                   <asp:ListItem Text = "Inactive">Inactive</asp:ListItem>

Here is the code for edit item template of formview

<asp:RadioButtonList ID="RadioButtonList3" runat="server"
                            SelectedValue = '<%# Bind("stat") %>'
                            Width="300px" TabIndex="3">
                            <asp:ListItem Text="Active" />

<asp:ListItem Text="Inactive" />

Note; stat is the column name for radiobutton list