Add new plugin errors

Hello folks,

My site has a few errors coming up when I go to the ‘plugins/add new’ page.
At the very top I get these errors listed:

Warning: Undefined property: stdClass::$plugin in /homepages/22/d930133688/htdocs/wp-includes/class-wp-list-util.php on line 168

(The above error is listed 4 times)

Warning: Cannot modify header information – headers already sent by (output started at /homepages/22/d930133688/htdocs/wp-includes/class-wp-list-util.php:168) in /homepages/22/d930133688/htdocs/wp-admin/admin-header.php on line 9

Can someone help me identify what could be wrong?

The whole site seems to work fine but it’s annoying and clearly something that should be fixed.
I’ve deactivated ALL plugins on my site but those errors still show when I go to the ‘add new’ page.

Thanks in advance