whisper: represent missing values as NaN
whisper: represent missing values as NaN

Using NaN allows us to distinguish the values lateron.

grobian/go-whisper,jjneely/go-whisper,lomik/go-whisper,grobian/go-whisper,lomik/go-whisper,robyoung/go-whisper,robyoung/go-whisper,jjneely/go-whisper