RFR: 8312533: JFR: No message for JFR.view when data is missing

[Erik Gahlin]

Could I have a review of a PR that adds a message when there is no data to view.

Testing: jdk/jdk/jfr

Thanks
Erik

-------------

Commit messages:
 - Initial

Changes: https://git.openjdk.org/jdk/pull/14998/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=14998&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8312533
  Stats: 80 lines in 2 files changed: 77 ins; 0 del; 3 mod
  Patch: https://git.openjdk.org/jdk/pull/14998.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/14998/head:pull/14998

PR: https://git.openjdk.org/jdk/pull/14998