links to Actions with Maybe's get literal Just in query params

[unhammer]

If I do

 | NewThingAction { redirect :: Maybe (Id Other) }  

and

        <a href={NewThingAction (Just user.id)}>New</a>

I get an unusable link

<a href="http://localhost:8000/NewThing?redirect=Just03142938-62d5-4de1-af90-49726ca98f35">

where I would expect

<a href="http://localhost:8000/NewThing?redirect=03142938-62d5-4de1-af90-49726ca98f35">

for the Just case and

<a href="http://localhost:8000/NewThing">

for the Nothing case

[amitaibu]

Started a PR in #1691