Please update dompdf

[Triskal]

I added this plugin to an empty Wordpress instance and tested it with PHP 8.1. It worked without issues. However, another project that had this plugin already, broke down with PHP 8.1. The issue has to do with dompdf trying to pass a null value as an argument to file_get_contents. I do not know why the issue presents itself in one instance and not the other, since the dompdf version is supposed to be the same in both. However, the issue is very easily fixed by just updating the packages.

[Triskal]

Oh, another thing: I have on two occasions now encountered the plugin also causing a fatal error, because DOMPDF_DEFAULT_PAPER_SIZE is not defined. This can be fixed by adding define('DOMPDF_DEFAULT_PAPER_SIZE', 'a4'); to wp-config.php, but properly fixing it would be preferrable.

[trevorbicewebdesign]

I am not affiliated with this project, but I had to update dompdf so I could use this plugin on a project I manage. I forked and opened a PR for those changes but I haven't seen any activity from the plugin developers. Anyway, here's the PR: #39