fix: Add flatten to advanced sightings add within objects
fix: Add flatten to advanced sightings add within objects

- without the flattening the advanced sighting add functionality couldn't be loaded

FIRSTdotorg/MISP,SteveClement/MISP,devnull-/MISP,SteveClement/MISP,FIRSTdotorg/MISP,devnull-/MISP,devnull-/MISP,Rafiot/MISP,MISP/MISP,FloatingGhost/MISP,TheDr1ver/MISP,MISP/MISP,SteveClement/MISP,FloatingGhost/MISP,FloatingGhost/MISP,devnull-/MISP,TheDr1ver/MISP,TheDr1ver/MISP,FloatingGhost/MISP,MISP/MISP,FIRSTdotorg/MISP,Rafiot/MISP,Rafiot/MISP,SteveClement/MISP,FIRSTdotorg/MISP,MISP/MISP,MISP/MISP,SteveClement/MISP,Rafiot/MISP,TheDr1ver/MISP