Throw 404 instead of 500 for non-existing static page listing
Throw 404 instead of 500 for non-existing static page listing

Some backends don't have a static page index listing. As this route
isn't linked from anywhere using these backends, this now throws 404,
not a 500.

phihag/adhocracy,phihag/adhocracy,DanielNeugebauer/adhocracy,alkadis/vcv,alkadis/vcv,phihag/adhocracy,liqd/adhocracy,liqd/adhocracy,DanielNeugebauer/adhocracy,alkadis/vcv,phihag/adhocracy,alkadis/vcv,DanielNeugebauer/adhocracy,alkadis/vcv,phihag/adhocracy,liqd/adhocracy,DanielNeugebauer/adhocracy,liqd/adhocracy,DanielNeugebauer/adhocracy