[jdk17u] RFR: 8269113: Javac throws when compiling switch (null)

[Ekaterina Vergizova]

I'd like to backport JDK-8269113 to 17u. It prevents AssertionError in javac.
The patch applies cleanly.
Tested with langtools tests, updated tests pass after applying the patch.

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Commit messages:
 - Backport 18870284084aaaf729640de0105ce21e253546b9

Changes: https://git.openjdk.java.net/jdk17u/pull/159/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk17u&pr=159&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8269113
  Stats: 45 lines in 4 files changed: 40 ins; 2 del; 3 mod
  Patch: https://git.openjdk.java.net/jdk17u/pull/159.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk17u pull/159/head:pull/159

PR: https://git.openjdk.java.net/jdk17u/pull/159