fix getJpegInfo to skip DHT marker

[rnigro-rwb]

Fixes #3318.

getJpegInfo now skips the DHT marker (0xc4) because that marker is not a SOF (start of frame) marker and therefore the segment to follow does not have the size information.

[HoekWax]

Hello @HackbrettXXX, is it possible to check and merge this fix ? We are multiple people facing this issue.

I can provide an image that creates the issue when used using addImage if you want me to.

Thanks.

[rnigro-rwb]

Linking PR to issue.

Fixes #3318

[HoekWax]

Hello @MrRio, can you or someone else review and merge this request ? Thanks

[racosa]

We also had this issue and this PR fixes it. Can someone merge this, please?

[rnigro-rwb]

@MrRio, @HackbrettXXX

To add to insight to this fix, the original getJpegInfo sites http://www.64lines.com/jpeg-width-height which itself sites a reference for header info: JPEG Header Information

As you can see here, Define Huffman table marker (FFC4), 0xC4 is a marker for the Huffman table.

My fix skips 0xC4 and adjusts the remaining Start of frame (SOFn) markers to be correct.