No error when accepting an already accepted invite

To reproduce:

invite a service admin
open the link in two separate browsers/private windows
both will show the "please accept this invite" dialog
accept one
try to accept the other; button will do nothing; network dashboard shows that https://acc.sram.surf.nl/api/service_invitations/accept returns a 404 (as expected), but apparently this is nog handled in the frontend.

SURFscz / SBS