Merge commit '456ffec35d55288d589aa1901919e038c3427f30'

* commit '456ffec35d55288d589aa1901919e038c3427f30':
  img2dec: correctly use the parsed value from -start_number

No change, start_number works fine without this change
and does not work with it

Merged-by: Michael Niedermayer <michaelni@gmx.at>