Allow manage-epson-fastfoto to stack Original and Back of Photo without Corrected version

[tonyflo]

trafficstars

It seems that unless all 3 versions of the image are present, the option --manage-epson-fastfoto=TRUE doesn't stack related photos.

1. specified-image-name.jpg (Original)
2. specified-image-name_a.jpg (Corrected)
3. specified-image-name_b.jpg (Back of Photo)

Epson software has the option to not do photo corrections, so some users might only end up with Original and Back of Photo.

1. specified-image-name.jpg (Original)
2. specified-image-name_b.jpg (Back of Photo)

It would be great if the option --manage-epson-fastfoto can stack the Original on top of the Back of Photo even if the Corrected doesn't exist.

[simulot]

This makes sens. On the todo list