OJS 3.3.0.13 and unofficial OpenAire Plugin

Hello everyone,

I’m having a small issue with an OJS instance (version 3.3.0.13).

I’ve uploaded this version of the openAIRE plugin:
https://github.com/munipress/openAIREstandard/tree/ojs-3-3-0_standard

When I try to check if the endpoint is working:
https://myojsurl/index.php/MYJOURNAL/oai?verb=ListRecords&metadataPrefix=oai_openaire

I get a blank page and the following error message in the logs:
Uncaught Error: Call to undefined method SubmissionFile::getFileSize() in /myojs/www/plugins/generic/openAIREstandard/OAIMetadataFormat_OpenAIREstandard.inc.php:226

So I commented out the lines around 226 in the

OAIMetadataFormat_OpenAIREstandard.inc.php file:
foreach ($galleys as $galley) {
                if($galley->getFile()){
                    $response .= "<datacite:size>" . round($galley->getFile()->getFileSize() / 1024 / 1024, 2) . " MB</datacite:size>\n";
                }
            }

Now the page displays correctly, but I have to give up the datacite:size tag for the galley size.

How can I solve this?

Thanks,