Relationship editor isn't correctly parsing attributes

https://beta.musicbrainz.org/release/622ad91b-873e-433e-9a6a-e55e70ee1cab/edit-relationships in German displays "zusätzlich ChorgesangChorgesang" for track 1.
The translated link phrase is "

{additional:zusätzlich}

{guest:Gast-} {solo:Solo-} {vocal} {vocal:|Stimme/Gesang}

" -

{vocal:|Stimme/Gesang}

means display "" if the attribute is set, "Stimme/Gesang" if it's not.