ofp-actions: Avoid buffer overread in BUNDLE action decoding.

Reported-at: https://bugs.chromium.org/p/oss-fuzz/issues/detail?id=9052
Signed-off-by: Ben Pfaff <blp@ovn.org>
Acked-by: Justin Pettit <jpettit@ovn.org>
parse_pop_vlan(struct ofpbuf *ofpacts)
{
    ofpact_put_STRIP_VLAN(ofpacts)->ofpact.raw = OFPAT_RAW11_POP_VLAN;
    return NULL;
}

parse_pop_vlan(struct ofpbuf *ofpacts)
{
    ofpact_put_STRIP_VLAN(ofpacts)->ofpact.raw = OFPAT_RAW11_POP_VLAN;
    return NULL;
}
