add filler zeroes when empty
add filler zeroes when empty

wltrimbl/kmerspectrumanalyzer,MG-RAST/kmerspectrumanalyzer,wltrimbl/kmerspectrumanalyzer,MG-RAST/kmerspectrumanalyzer,MG-RAST/kmerspectrumanalyzer,wltrimbl/kmerspectrumanalyzer