also break out of the loop on reads of 0 bytes (otherwise we loop on bad devices).
also break out of the loop on reads of 0 bytes (otherwise we loop
on bad devices).


git-svn-id: 40dd595c6684d839db675001a64203a1457e7319@10060 67ed7778-7388-44ab-90cf-0a291f65f57c

gphoto/libgphoto2.OLDMIGRATION,gphoto/libgphoto2.OLDMIGRATION,gphoto/libgphoto2.OLDMIGRATION,gphoto/libgphoto2.OLDMIGRATION