diff plugin/FeatureExtractionPluginFactory.cpp @ 184:5a916fee6d2d

* Handle generator transforms (plugins whose channel count isn't dependent on
  number of audio inputs, as they have none)
* Be less keen to suspend writing FFT data in spectrogram repaint -- only do it
  if we find we actually need to query the FFT data (i.e. we aren't repainting
  an area that hasn't been generated at all yet)