Posterized output silently fail when default compression is JPEG

[hfiguiere]

Set the output compression for colour to JPEG

Posterize some of the colour / grayscale images

Generate the output.

This posterized images fail to save. No error shown.

The console show the following: JPEGSetupEncode: PhotometricInterpretation 3 not allowed for JPEG.

Expected

• show an error in case of failure: there is still a slight hint that it failed as the ? in the thumbnail is here.
• automatically fallback to lzw for for this PhotometricInterpretation