Don't write empty kern feature.
Don't write empty kern feature.

googlefonts/ufo2ft,adrientetar/ufo2fdk,jamesgk/ufo2fdk,anthrotype/ufo2fdk,jamesgk/ufo2ft,typemytype/ufo2fdk,moyogo/ufo2ft,moyogo/ufo2fdk,bitforks/ufo2fdk,benkiel/ufo2fdk,typesupply/ufo2fdk,googlei18n/ufo2ft,daltonmaag/ufo2fdk