RFR: 8326915: NPE when a validating parser is restricted

[Joe Wang]

Fix a NPE when a validating parser is restricted by the JDKCatalog resolve property. Also slightly improved the error msg with the catalog name.

Test: new test added
         existing test CatalogSupport5 would fail without the Null check on ErrorReporter. It's a separate issue not covered by this fix.

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Commit messages:
 - 8326915: NPE when a validating parser is restricted

Changes: https://git.openjdk.org/jdk/pull/18071/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=18071&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8326915
  Stats: 116 lines in 5 files changed: 101 ins; 0 del; 15 mod
  Patch: https://git.openjdk.org/jdk/pull/18071.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/18071/head:pull/18071

PR: https://git.openjdk.org/jdk/pull/18071