[jdk16] RFR: JDK-8241353: NPE in ToolProvider.getSystemJavaCompiler

[Jonathan Gibbons]

Trivial fix to avoid NPE by using `Objects.equals` instead of direct `String.equals`

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Commit messages:
 - JDK-8241353: NPE in ToolProvider.getSystemJavaCompiler

Changes: https://git.openjdk.java.net/jdk16/pull/32/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk16&pr=32&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8241353
  Stats: 4 lines in 1 file changed: 0 ins; 1 del; 3 mod
  Patch: https://git.openjdk.java.net/jdk16/pull/32.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk16 pull/32/head:pull/32

PR: https://git.openjdk.java.net/jdk16/pull/32