Fix uncaught JSONDecodeError on /prefix/add
Fix uncaught JSONDecodeError on /prefix/add

/prefix/add calls xhr/list_pool without body, so there is no attributes
to filter for and decoding the inexistent JSON fails.

garberg/NIPAP,SpriteLink/NIPAP,garberg/NIPAP,garberg/NIPAP,SpriteLink/NIPAP,SpriteLink/NIPAP,SpriteLink/NIPAP,SpriteLink/NIPAP,SpriteLink/NIPAP,garberg/NIPAP,garberg/NIPAP,garberg/NIPAP