WCGA Validation error

Hello I have an issue with wcga validation using https://wave.webaim.org/
the error I got is a hidden empty button on the header the reference code is the following

<div id=”INDContent” class=”INDpopupContent”></div>
ARIA tabindexEmpty button
<button id=”INDCloseBtn” class=”INDpopupConfirm” tabindex=”0″></button>
</div>

Please advice,

Apostolos

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