Avoid "spawning" of extra mini cal divs

add_filter( 'tribe_get_template_part_content', 'mini_cal_stop_div_spawning', 10, 5 );

function mini_cal_stop_div_spawning( $html, $template, $file, $slug, $name ) {
    // Only interfere with the mini calendar widget
    if ( 'pro/widgets/mini-calendar-widget.php' !== $template ) return $html;

    // ... and only during ajax requests
    if ( ! defined('DOING_AJAX') || ! DOING_AJAX ) return $html;

    // Figure out which parts we want to discard and which we want to keep
    $opening_div = '<div class="tribe-mini-calendar-wrapper">';
    $closing_div = '</div>';
    $start = strpos( $html, $opening_div ) + strlen( $opening_div );
    $close = strrpos( $html, $closing_div );

    // Return the good part
    return substr( $html, $start, $close - $start );
}