RFR: Remove redundant null checks [v11]

[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:

  improving tests

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

Changes:
  - all: https://git.openjdk.org/valhalla/pull/1947/files
  - new: https://git.openjdk.org/valhalla/pull/1947/files/69e7b3ac..7100d19f

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=valhalla&pr=1947&range=10
 - incr: https://webrevs.openjdk.org/?repo=valhalla&pr=1947&range=09-10

  Stats: 7 lines in 1 file changed: 7 ins; 0 del; 0 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