RFR: Remove redundant null checks [v10]

[Vicente Romero]

> some of the null checks javac generates are redundant and can be removed

Vicente Romero has updated the pull request incrementally with one additional commit since the last revision:

  addressing review comments

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Changes:
  - all: https://git.openjdk.org/valhalla/pull/1947/files
  - new: https://git.openjdk.org/valhalla/pull/1947/files/c0d70e69..69e7b3ac

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=valhalla&pr=1947&range=09
 - incr: https://webrevs.openjdk.org/?repo=valhalla&pr=1947&range=08-09

  Stats: 13 lines in 2 files changed: 7 ins; 4 del; 2 mod
  Patch: https://git.openjdk.org/valhalla/pull/1947.diff
  Fetch: git fetch https://git.openjdk.org/valhalla.git pull/1947/head:pull/1947

PR: https://git.openjdk.org/valhalla/pull/1947