RFR: 8366522: CodeSource.getCodeSigners() throws NPE within empty certs [v7]

[Kirill Shirokov]

> The new tests cover only NPE scenarios.

Kirill Shirokov has updated the pull request incrementally with one additional commit since the last revision:

  Fixed a typo in a comment

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Changes:
  - all: https://git.openjdk.org/jdk/pull/27105/files
  - new: https://git.openjdk.org/jdk/pull/27105/files/a134a9ae..64673e1f

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=27105&range=06
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=27105&range=05-06

  Stats: 1 line in 1 file changed: 0 ins; 0 del; 1 mod
  Patch: https://git.openjdk.org/jdk/pull/27105.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/27105/head:pull/27105

PR: https://git.openjdk.org/jdk/pull/27105