Steps to replicate the issue (include links if applicable):
Not sure, I guess some kind of malformed Accept-Language header produces it.
What happens?:
[21-Oct-2022 10:32:34 Europe/Helsinki] PHP Notice: Undefined offset: 1 in /data/srv/mediawiki/tieteentermipankki.fi/tags/2022-10-01_15:28:07/includes/libs/http/HttpAcceptParser.php on line 43 2022-10-21 07:32:34 [xxx]: [Y1JLEiArXv1gs1it4l8X6AAAABE] /w/rest.php/tieteentermipankki.fi/v3/transform/wikitext/to/html/[xxx] PHP Notice: Undefined offset: 1 #0 /data/srv/mediawiki/tieteentermipankki.fi/tags/2022-10-01_15:28:07/includes/libs/http/HttpAcceptParser.php(43): MWExceptionHandler::handleError(integer, string, string, integer, array) #1 /data/srv/mediawiki/tieteentermipankki.fi/tags/2022-10-01_15:28:07/extensions/VisualEditor/includes/VEParsoid/src/Rest/Handler/ParsoidHandler.php(298): Wikimedia\Http\HttpAcceptParser->parseAccept(string) #2 /data/srv/mediawiki/tieteentermipankki.fi/tags/2022-10-01_15:28:07/extensions/VisualEditor/includes/VEParsoid/src/Rest/Handler/TransformHandler.php(91): VEParsoid\Rest\Handler\ParsoidHandler->acceptable(array) #3 /data/srv/mediawiki/tieteentermipankki.fi/tags/2022-10-01_15:28:07/includes/Rest/Router.php(414): VEParsoid\Rest\Handler\TransformHandler->execute() #4 /data/srv/mediawiki/tieteentermipankki.fi/tags/2022-10-01_15:28:07/includes/Rest/Router.php(338): MediaWiki\Rest\Router->executeHandler(VEParsoid\Rest\Handler\TransformHandler) #5 /data/srv/mediawiki/tieteentermipankki.fi/tags/2022-10-01_15:28:07/includes/Rest/EntryPoint.php(168): MediaWiki\Rest\Router->execute(MediaWiki\Rest\RequestFromGlobals) #6 /data/srv/mediawiki/tieteentermipankki.fi/tags/2022-10-01_15:28:07/includes/Rest/EntryPoint.php(133): MediaWiki\Rest\EntryPoint->execute() #7 /data/srv/mediawiki/tieteentermipankki.fi/tags/2022-10-01_15:28:07/rest.php(31): MediaWiki\Rest\EntryPoint::main() #8 {main}
What should have happened instead?:
No PHP notices
Software version (skip for WMF-hosted wikis like Wikipedia):
MediaWiki 1.38.4
Other information (browser name/version, screenshots, etc.):