RFR: 6846: Parser needs to skip events with no metadata [v3]

[Marcus Hirt]

> Also fixing some javadoc errors.

Marcus Hirt has updated the pull request incrementally with one additional commit since the last revision:

  Fix

-------------

Changes:
  - all: https://git.openjdk.java.net/jmc/pull/128/files
  - new: https://git.openjdk.java.net/jmc/pull/128/files/f7f25666..b5467758

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jmc&pr=128&range=02
 - incr: https://webrevs.openjdk.java.net/?repo=jmc&pr=128&range=01-02

  Stats: 11 lines in 1 file changed: 1 ins; 10 del; 0 mod
  Patch: https://git.openjdk.java.net/jmc/pull/128.diff
  Fetch: git fetch https://git.openjdk.java.net/jmc pull/128/head:pull/128

PR: https://git.openjdk.java.net/jmc/pull/128