ul tag cause error

causes a settings save error below. If you remove these html tags the error goes away.

\Warning: A non-numeric value encountered in /www/wp-content/plugins/send-pdf-for-contact-form-7/mpdf/Tag.php on line 1889 Warning: A non-numeric value encountered in /www/wp-content/plugins/send-pdf-for-contact-form-7/mpdf/Tag.php on line 1889 Warning: A non-numeric value encountered in /www/wp-content/plugins/send-pdf-for-contact-form-7/mpdf/Tag.php on line 1889 Warning: A non-numeric value encountered in /www/wp-content/plugins/send-pdf-for-contact-form-7/mpdf/Tag.php on line 1889 Warning: A non-numeric value encountered in /www/wp-content/plugins/send-pdf-for-contact-form-7/mpdf/Tag.php on line 2006 Warning: A non-numeric value encountered in /www/wp-content/plugins/send-pdf-for-contact-form-7/mpdf/Tag.php on line 2006 Warning: A non-numeric value encountered in /www/wp-content/plugins/send-pdf-for-contact-form-7/mpdf/mpdf.php on line 6387 Warning: A non-numeric value encountered in /www/wp-content/plugins/send-pdf-for-contact-form-7/mpdf/Tag.php on line 2003 Warning: A non-numeric value encountered in /www/wp-content/plugins/send-pdf-for-contact-form-7/mpdf/mpdf.php on line 6387 Warning: A non-numeric value encountered in /www/wp-content/plugins/send-pdf-for-contact-form-7/mpdf/Tag.php on line 2003 Warning: A non-numeric value encountered in /www/wp-content/plugins/send-pdf-for-contact-form-7/mpdf/mpdf.php on line 6387 Warning: A non-numeric value encountered in /www/wp-content/plugins/send-pdf-for-contact-form-7/mpdf/Tag.php on line 2003 Warning: A non-numeric value encountered in /www/wp-content/plugins/send-pdf-for-contact-form-7/mpdf/mpdf.php on line 6387