Delete row from ASP.Net Repeater Error: Object reference not set to an instance of an object

I follow the steps in this example

https://www.aspsnippets.com/Articles/Implement-Delete-with-Confirmation-in-ASPNet-Repeater-control.aspx

But i got error :

Object reference not set to an instance of an object.

here's where the exception happen

and here's my code in the design:

<asp:Repeater ID="rpdetails" runat="server">
    <HeaderTemplate>
 
        <table class="table table-hover" id="tblData"  >
            <tr class="table-success"">
              <th></th>  <th class="text-nowrap">Report Time </th><th class="text-nowrap">Reported by</th><th class="text-nowrap">Current Position</th><th>Procedure</th><th class="text-nowrap">Taken by</th><th class="text-nowrap">Problem desc</th><th>Shift</th><th>Problem State</th>
            </tr>
    </HeaderTemplate>
    <ItemTemplate><tr dir="ltr">
           <td align="left">
               <asp:LinkButton ID="lnkDelete" Text="Delete" runat="server" OnClientClick="return confirm('Do you want to delete this Report?');"
                    OnClick="DeleteRep" />                   
            </td>
            <td>
                <asp:Label ID="time" runat="server" Text='<%# Eval("reporting_time") %>' />
            </td>
            <td>
                <asp:Label ID="Label1" runat="server" Text='<%# Eval("repby") %>' />
            </td>
            <td align="left">
                <asp:Label ID="Label2" runat="server" Text='<%# Eval("curr_pos") %>' />
            </td>
            <td align="left">
                <asp:Label ID="pro" runat="server" Text='<%# Eval("procedure_taken") %>' />
            </td>
            <td>
                <asp:Label ID="Label3" runat="server" Text='<%# Eval("takenBy") %>' />
            </td>
            <td align="left">
                <asp:Label ID="desc" runat="server" Text='<%# Eval("pro_desc") %>' />
            </td>
            <td>
                <asp:Label ID="Label4" runat="server" Text='<%# Eval("shift") %>' />
            </td>            
            <td align="left">
                <asp:Label ID="Label6" runat="server" Text='<%# Eval("problem_status") %>' />
            </td>            
        </tr></ItemTemplate>
    <FooterTemplate>
        </table>      
    </FooterTemplate>
    </asp:Repeater>

   Protected Sub DeleteRep(s As Object, e As EventArgs)
       Dim r As New problem() 
       Dim repId As Integer = Integer.Parse(TryCast(TryCast(s, LinkButton).NamingContainer.FindControl("pIDlbl"), Label).Text)      
       Dim result As String = r.removeP(Session("userId"), repId)
       Dim p As New device()
       rpdetails.DataSource = p.getAllProblems()
       rpdetails.DataBind()
   End Sub