Fluent editor adds back removed variant in multi-variant string

[flodolo]

https://pontoon.mozilla.org/it/firefox-relay-website/en/misc.ftl/?string=248079

This is the current string

offer-countdown-timer-alt =
    { $remaining_days ->
        [0]
            { $remaining_hours ->
                [1] 1 ora rimanente
               *[other] { $remaining_hours } ore rimanenti
                [0] { "" }
            }
        [1]
            { $remaining_hours ->
                [1] 1 giorno e 1 ora rimanenti
               *[other] 1 giorno e { $remaining_hours } ore rimanenti
                [0] 1 giorno rimanente
            }
       *[other]
            { $remaining_hours ->
                [1] { $remaining_days } giorni e 1 ora rimanenti
               *[other] { $remaining_days } giorni e { $remaining_hours } ore rimanenti
                [0] { $remaining_days } giorni rimanenti
            }
    }

If I remove the empty 0 variant and try to submit, I get an error (Empty translation). When I switch back to the standard UI, Pontoon adds back the empty 0 form.