whisper out of range time range cause incorrect value to be returned

When specifying a range in the future, fetch_file accepts the range as ok and returns an incorrect timeinfo with an end < start.

How to reproduce :
take any timeseries
Call fetch_file with
   from = now + 1h
   until = now + 3h

fetch_file returns a series of NONE values correct with a timeinfo like this:

  start = from
  end = now

As from is in the future, the timeinfo returned has end < start which is cleary a bug.