fix(hip): make() without parameters writes Header Length 0, below the RFC 7401 minimum of 4 #1189

Describe the bug
HIP.make(parameters=None) writes Header Length 0 (parameters_value, length = [], 0). RFC 7401 §5.1 says the minimum is 4: the field counts 8-octet units excluding the first 8, and every header carries both 16-octet HITs. Construction then fails in its own re-parse. read computes _prml = (0 - 4) * 8 = -32, which is truthy, so it calls _read_hip_param(-32) and raises ProtocolError: HIPv2: invalid format (hip.py:792).

To Reproduce
On origin/main, run HIP(parameters=None, version=2, next=59, packet=1, checksum=b'\x00\x00', controls_anonymous=False, shit=0, rhit=0, payload=b''). It packs 3b00012100000000… with a length byte of 0 and raises as described. HIPv1 behaves the same way.

Expected behavior
A parameterless header is 40 octets with Header Length 4, and it parses back.

Found by the #1188 worker. The #1188 cross-review reproduced it and checked RFC 7401 §5.1.