RFR: 8236671: NullPointerException in JKS keystore

[Sean Coffey]

Trivial enough change. Improved the exception thrown from JceKeyStore also.

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Commit messages:
 - Fix white space
 - 8236671: NullPointerException in JKS keystore

Changes: https://git.openjdk.java.net/jdk/pull/3588/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=3588&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8236671
  Stats: 17 lines in 3 files changed: 14 ins; 0 del; 3 mod
  Patch: https://git.openjdk.java.net/jdk/pull/3588.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/3588/head:pull/3588

PR: https://git.openjdk.java.net/jdk/pull/3588