Update tcpdf.php for undefined array key

[medarob]

Core: Error handler (FE): PHP Warning: Undefined array key 0 in /var/www/typo3/vendor/tecnickcom/tcpdf/tcpdf.php line 20833
Core: Error handler (FE): PHP Warning: Undefined array key -1 in /var/www/typo3/vendor/tecnickcom/tcpdf/tcpdf.php line 20689
Core: Error handler (FE): PHP Warning: Undefined array key 0 in /var/www/typo3/vendor/tecnickcom/tcpdf/tcpdf.php line 19318

[CLAassistant]

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