Fix 'create new proposal' link for relative_url
Fix 'create new proposal' link for relative_url

Addendum to e74eaf6b0f0bda02dd3a69ac2e0065c6071c6503

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