set nfft =0 on invalid file
set nfft =0 on invalid file

joshblum/eeg-spectrogram,joshblum/eeg-toolkit,joshblum/eeg-spectrogram,joshblum/eeg-toolkit,joshblum/eeg-toolkit,joshblum/eeg-toolkit,joshblum/eeg-spectrogram,joshblum/eeg-spectrogram,joshblum/eeg-spectrogram,joshblum/eeg-toolkit