How to fix an error when clicking on a CustomButton in Visual Studio?

Question

JavaScript

When clicking on the CustomButton, the following message appears:

<script>
function CustomButtonClickMSQQ_C(s, e) {
        debugger;
        if (e.buttonID == 'btnInsertMI') {
            pcMeasurementsChoiceMSQQ.SetContentUrl('PageProgress.aspx?Page=Passport/FormMSQQ_MI.aspx?id=' + hfBM.Get('msys_id').toString());
            pcMeasurementsChoiceMSQQ.Show();
        }
    }
</script>
<dx:ASPxHiddenField ID="hfBM" ClientInstanceName="hfBM" runat="server">
</dx:ASPxHiddenField>
<div id="msgUserAcc">
</div>
<asp:FormView ID="fvComposition" DefaultMode="ReadOnly" runat="server" Width="100%">
    <ItemTemplate>
        <dx:ASPxGridView Width="25%" ID="gvCompositionMSQQ" runat="server" AutoGenerateColumns="False"
            ClientInstanceName="gvCompositionMSQQ" KeyFieldName="msys_block_id" DataSourceID="ODS_CompositionMSQQ"
            OnRowInserted="FocusRow" OnCustomErrorText="CustomErrorText">
            <ClientSideEvents CustomButtonClick="CustomButtonClickMSQQ_C" CallbackError="function(s, e) { OnCallbackErr('msgUser', e); }" />