The description of strings.FieldsFunc was fixed some time ago by
https://golang.org/cl/3814041, but the equivalent change to bytes.FieldsFunc
was forgotten.

The last sentence of the description should read
  "If all code points in s satisfy f(c) or s is empty, an empty slice is returned."
instead of
  "If no code points in s satisfy f(c), an empty slice is returned."

Which version are you using?  (run 'go version')
  Go 1.2