After pushing the Invoice-button, (see attachment) i see the following message:

Notice: Undefined offset: 16 in /home/mystore/public_html/system/mpdf/mpdf.php on line 21162Notice: Undefined offset: 1 in /home/mystore/public_html/system/mpdf/mpdf.php on line 21193Warning: Cannot modify header information - headers already sent by (output started at /home/mystore/public_html/system/library/app.php:96) in /home/mystore/public_html/system/mpdf/mpdf.php on line 8314Warning: Cannot modify header information - headers already sent by (output started at /home/mystore/public_html/system/library/app.php:96) in /home/mystore/public_html/system/mpdf/mpdf.php on line 1706mPDF error: Some data has already been output to browser, can't send PDF file

I changed rule number 813 in invoice.php into invoice_data but still the message wil appear.

Regards Manfred.