I updated from MediaWiki 1.31 to 1.34 and thus from Contributors "2.0 (bf42ccf) 03:30, 22. Nov. 2017" to "2.0 (04de8a2) 08:36, 10. Sep. 2019".
After running
php extensions/Contributors/maintenance/PopulateContributorsTable.php
the special page "Special:Contributors" works as expected.
But the inclusion with {{Special:Contributors/Article}} generates no output at all. It only shows 2 warnings:
Warning: array_keys() expects parameter 1 to be array, null given in /html/site/mediawiki/extensions/Contributors/includes/Contributors.php on line 187 Warning: Invalid argument supplied for foreach() in /html/site/mediawiki/extensions/Contributors/includes/Contributors.php on line 196 `
Changing to the master version of the extension doesn't fix the error.
Update: I'm not the only one with this error message. See the third pic on https://github.com/wikimedia/mediawiki-extensions-Contributors/issues/3.
Who can fix this please?