[IPV4/6]: Fix UFO error propagation

When ufo_append_data fails err is uninitialized, but returned back.
Strangely gcc doesn't notice it.

Coverity #901 and #902

Signed-off-by: Patrick McHardy <kaber@trash.net>
Signed-off-by: David S. Miller <davem@davemloft.net>
2 files changed