RFR: 8299864: ZipFileStore#supportsFileAttributeView(String) doesn't throw NPE

[Per Minborg]

This PR proposes to add null-checking for some parameter arguments in `ZipFileStore`.

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Commit messages:
 - Check null invariants

Changes: https://git.openjdk.org/jdk/pull/11926/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=11926&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8299864
  Stats: 49 lines in 2 files changed: 26 ins; 1 del; 22 mod
  Patch: https://git.openjdk.org/jdk/pull/11926.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/11926/head:pull/11926

PR: https://git.openjdk.org/jdk/pull/11926