Fiddler writes a zero-byte raw/NN_s.txt (or _c.txt) for a session that
never got that message. The decoder passed it to the HTTP parser, which
found no header/body separator and rejected the whole archive, so no
session could be read even with --record.
Report a zero-byte request or response member as null, like a missing
member, keep it in location.members, and add a per-record limitation
that says only that the stored member is empty. Non-empty malformed
members are still rejected.
Fixes#5411
amyanger
b0a554cc3a