fix(ipv6-opts): SMF_DPD H-DPD with an empty hav raises IndexError instead of ProtocolError #1193

Describe the bug
_make_opt_smf_dpd reads hav[0] with no length check, so an H-DPD option built with an empty hav raises a bare IndexError rather than ProtocolError. The access is at pcapkit/protocols/internet/hopopt.py:1678 on main; ipv6_opts.py has the same line.

To Reproduce
On origin/main (or the #1192 branch):
HOPOPT(next=59, options=[(Option.SMF_DPD, {'mode': SMFDPDMode.H_DPD, 'hav': b''})]) → IndexError: index out of range. IPv6_Opts behaves the same.

Expected behavior
An empty Hash Assist Value is rejected with an in-library ProtocolError naming the option, matching the other SMF_DPD validation errors.

The #1190 worker found this, and the #1192 cross-review reproduced it on both branches. I re-ran it on the #1192 branch.