Undefined offset: -1 in mpdf/vendor/mpdf/mpdf/src/Tag/BlockTag.php on line 118

When entering the admin panel I recieve a lot of error messages similar to:

Notice: Undefined offset: -1 in /home/fwwelgsd/public_html/arcocandas.es/wp-content/plugins/send-pdf-for-contact-form-7/mpdf/vendor/mpdf/mpdf/src/Tag/BlockTag.php on line 118

Notice: Undefined offset: 0 in /home/fwwelgsd/public_html/arcocandas.es/wp-content/plugins/send-pdf-for-contact-form-7/mpdf/vendor/mpdf/mpdf/src/Tag/BlockTag.php on line 118

Notice: Undefined offset: 1 in /home/fwwelgsd/public_html/arcocandas.es/wp-content/plugins/send-pdf-for-contact-form-7/mpdf/vendor/mpdf/mpdf/src/Tag/BlockTag.php on line 118

Notice: Undefined offset: 2 in /home/fwwelgsd/public_html/arcocandas.es/wp-content/plugins/send-pdf-for-contact-form-7/mpdf/vendor/mpdf/mpdf/src/Tag/BlockTag.php on line 118

And several more…