At least old Xen net backends seem to send frags with no real data
sometimes. In case such a fragment happens to occur with the frag limit
already reached the frontend will BUG currently even if this situation
is easily recoverable.
Modify the BUG_ON() condition accordingly.
Tested-by: Dietmar Hahn <dietmar.hahn@ts.fujitsu.com> Signed-off-by: Juergen Gross <jgross@suse.com> Signed-off-by: David S. Miller <davem@davemloft.net>