[code-reflection] RFR: Null check only when selector expression of switch expression is of reference type

[Mourad Abbay]

Generate lowered form of switch expression that check if the selector expression is null only when the selector expression has type reference.

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Commit messages:
 - Null check only when selector expression of switch expression is of reference type.

Changes: https://git.openjdk.org/babylon/pull/112/files
  Webrev: https://webrevs.openjdk.org/?repo=babylon&pr=112&range=00
  Stats: 13 lines in 1 file changed: 4 ins; 7 del; 2 mod
  Patch: https://git.openjdk.org/babylon/pull/112.diff
  Fetch: git fetch https://git.openjdk.org/babylon.git pull/112/head:pull/112

PR: https://git.openjdk.org/babylon/pull/112