At certain wikis, I get this error message when trying to access [[Special:EditWatchlist/raw]]
Exception encountered, of type "Wikimedia\Assert\ParameterTypeException"
E.g.
https://commons.wikimedia.org/wiki/Special:EditWatchlist/raw
https://www.mediawiki.org/wiki/Special:EditWatchlist/raw
https://meta.wikimedia.org/wiki/Special:EditWatchlist/raw
https://pt.wikibooks.org/wiki/Special:EditWatchlist/raw
It seems to be restricted to 1.27.0-wmf.18 for wikis that use Flow, and it is dependent on the account having a Flow topic on their watchlist.
I.e. as of today it does not affect
https://en.wikipedia.org/wiki/Special:EditWatchlist/raw
https://en.wikiquote.org/wiki/Special:EditWatchlist/raw (Flow not used here)
https://fr.wikibooks.org/wiki/Special:EditWatchlist/raw (Flow not used here)
and does not affect a vanilla test account at Commons until I watchlist a topic, e.g. https://commons.wikimedia.org/wiki/Topic:Smtrcre7hhh81d4z