[Kesavamoorthig06]

Seeking to an MPO frame whose offset points at data that isn't a JPEG stream crashes with an unhandled IndexError:

  File ".../PIL/MpoImagePlugin.py", line 164, in seek
    JpegImagePlugin.JpegImageFile._open(self)
  File ".../PIL/JpegImagePlugin.py", line 379, in _open
    i = s[0]
IndexError: index out of range

The marker scan in JpegImageFile._open skips non-0xFF junk one byte at a time:

else:
    # Skip non-0xFF junk
    s = self.fp.read(1)
    continue

If the file ends while skipping junk, read(1) returns b"" and the next loop iteration does s[0] on empty bytes. When _open runs during Image.open, ImageFile wraps that error, but MpoImageFile.seek calls _open directly, so the raw IndexError escapes to the caller.

This PR raises SyntaxError("unexpected end of file") when the scan runs out of data, both in the junk-skip path and when EOF cuts a 0xFF marker in half (which otherwise fails i16 with a struct.error).

Reproducer: Tests/images/mpo_junk_frame.mpo (added in this PR) is a normal two-frame MPO whose second-frame offset was hexedited to point at data that isn't a JPEG stream. On unpatched Pillow, im.seek(1) raises IndexError; with this PR it raises SyntaxError.

Tests added: test_mp_junk_frame_offset in Tests/test_file_mpo.py and test_eof_while_skipping_junk in Tests/test_file_jpeg.py.

[radarhere]

I've opted to exit the loop, instead of raising a specific error. I think this is more inline with how Pillow behaves, and still solves your problem.