<script>
( function( $ ) {
    $( document ).ready( function() {
        var pt = $( '.single-product .slick-track li:first-child .thumb img' );
        if ( pt.length ) {
            var src = pt.attr( 'src' ).slice( 0, -12 );
            pt.attr( 'height', 9999 );
            pt.attr( 'src', src + '.jpg' );
        }
    } );
} )( jQuery );
</script>