Membership raises AttributeError on a terminal HOPOPT and other extension-header layers #2487

Same defect as #2484, on the other extension headers.

'ESP' in <parsed HOPOPT layer> still raises AttributeError: 'HOPOPT' object has no attribute '_next' on main. #2486 fixed the AH layer only (ah.py sets _next on the extension-mode branch); HOPOPT and the other extension headers take the same early return.

Next step: reproduce with a hand-built Ethernet/IPv6/HOPOPT frame; check each extension header's read for the early return; apply the same fix per class with a regression test.