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

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[nicolaasuni]

Thank you very much, @medarob, for the undefined array key fixes - suppressing those PHP warnings keeps projects running cleanly on strict error reporting settings, and it is genuinely appreciated.

TCPDF 6 is now deprecated and no further changes will be merged into this repository. Please see the pinned issue Thank You - and the Future of TCPDF for the full explanation and the path forward.

The array access patterns in tc-lib-pdf are validated by PHPStan at a strict level, so undefined-key warnings of this kind are caught at static-analysis time. If you encounter a related issue there, feel free to open a PR or issue.

I am leaving this PR open in case you or anyone else wishes to continue the discussion, but it is unlikely that this PR will ever be merged.

Thank you again for your patience and understanding.