citationStyleLanguage plugin problem

Describe the issue or problem
I’m facing the warring below and it’s repeating itself every minute in the error log file. I reached the developer of the citationStyleLanguage plugin and explained the problem for him and his response was " I’m not familiar with OJS. I need a Citation Style and the json formatted metadata." my question is how can I determine the Citation Style and the json format in OJS

 PHP Warning:  Attempt to read property "single" on null in /server/journal.com/public_html/plugins/generic/citationStyleLanguage/lib/vendor/seboettg/citeproc-php/src/Rendering/Date/DatePart.php on line 227
 PHP Warning:  Attempt to read property "single" on null in /server/journal.com/public_html/plugins/generic/citationStyleLanguage/lib/vendor/seboettg/citeproc-php/src/Rendering/Date/DatePart.php on line 227
 PHP Warning:  Attempt to read property "single" on null in /server/journal.com/public_html/plugins/generic/citationStyleLanguage/lib/vendor/seboettg/citeproc-php/src/Rendering/Date/DatePart.php on line 227
 PHP Warning:  Attempt to read property "single" on null in /server/journal.com/public_html/plugins/generic/citationStyleLanguage/lib/vendor/seboettg/citeproc-php/src/Rendering/Date/DatePart.php on line 227

What application are you using?
I’m using OJS 3.3.0-13 with PHP 8.0

Additional information
Please add any screenshots, logs or other information we can use to investigate this problem.