use safe division in cluster summarizer
use safe division in cluster summarizer

escherba/lsh-hdc,escherba/lsh-hdc,pombredanne/lsh-hdc,pombredanne/lsh-hdc,pombredanne/lsh-hdc,escherba/lsh-hdc,pombredanne/lsh-hdc,escherba/lsh-hdc,escherba/lsh-hdc,pombredanne/lsh-hdc