fix: [clusterRelations:fork_tree] Prevent division by 0
fix: [clusterRelations:fork_tree] Prevent division by 0

MISP/MISP,MISP/MISP,SteveClement/MISP,MISP/MISP,SteveClement/MISP,MISP/MISP,SteveClement/MISP,SteveClement/MISP,MISP/MISP,SteveClement/MISP