message: Fix wrong expectation of image info
  The decoder unwrapped the info struct from the jpeg decoder. This is not
  guaranteed to return Some, e.g. when not even the header of the jpeg
  was parsed correctly.
diff: @@ -21,7 +21,9 @@ impl<R: Read> JpegDecoder<R> {
  let mut decoder = jpeg::Decoder::new(r);
  decoder.read_info().map_err(ImageError::from_jpeg)?;
  - let mut metadata = decoder.info().unwrap();
  + let mut metadata = decoder.info().ok_or_else(|| {
  + ImageError::Decoding(DecodingError::from_format_hint(ImageFormat::Jpeg.into()))
  + })?;
  // We convert CMYK data to RGB before returning it to the user.
  if metadata.pixel_format == jpeg::PixelFormat::CMYK32 {
  