Fix from_vector for single channel images
Fix from_vector for single channel images

The new image shape has already been created with at least one
channel, so we don't want to append another.

jabooth/menpo-archive,menpo/menpo,grigorisg9gr/menpo,grigorisg9gr/menpo,yuxiang-zhou/menpo,yuxiang-zhou/menpo,mozata/menpo,mozata/menpo,patricksnape/menpo,menpo/menpo,mozata/menpo,patricksnape/menpo,mozata/menpo,jabooth/menpo-archive,patricksnape/menpo,menpo/menpo,jabooth/menpo-archive,yuxiang-zhou/menpo,grigorisg9gr/menpo,jabooth/menpo-archive