message: Fix missing check for line ending at anymap header
diff: @@ -281,7 +281,12 @@ trait HeaderReader: BufRead {
  let mut tupltype: Option<String> = None;
  loop {
  line.truncate(0);
  - self.read_line(&mut line).map_err(ImageError::IoError)?;
  + let len = self.read_line(&mut line).map_err(ImageError::IoError)?;
  + if len == 0 {
  + return Err(ImageError::FormatError(
  + format!("Unexpected end of pnm header"),
  + ))
  + }
  if line.as_bytes()[0] == b'#' {
  continue;
  }
  