Fixed inverted logic; abort if there aren't any transformed thumbnails.
Fixed inverted logic; abort if there aren't any transformed thumbnails.

lordofhyphens/Slic3r,pieis2pi/Slic3r,alexrj/Slic3r,alexrj/Slic3r,lordofhyphens/Slic3r,lordofhyphens/Slic3r,alexrj/Slic3r,pieis2pi/Slic3r,alexrj/Slic3r,lordofhyphens/Slic3r,alexrj/Slic3r,curieos/Slic3r,curieos/Slic3r,pieis2pi/Slic3r,alexrj/Slic3r,pieis2pi/Slic3r,curieos/Slic3r,curieos/Slic3r,curieos/Slic3r,lordofhyphens/Slic3r,pieis2pi/Slic3r,pieis2pi/Slic3r,lordofhyphens/Slic3r,curieos/Slic3r