RFR: 7482: Confusing display of stack traces when selecting event types with no events

[Jean-Philippe Bempel]

…th no events

In EventBrowser page, when there is no selection all events are
considered but if there is a selection we filtered events based on
this selection event if there is no events

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Commit messages:
 - 7482: Confusing display of stack traces when selecting event types with no events

Changes: https://git.openjdk.java.net/jmc/pull/344/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jmc&pr=344&range=00
  Issue: https://bugs.openjdk.java.net/browse/JMC-7482
  Stats: 29 lines in 2 files changed: 28 ins; 0 del; 1 mod
  Patch: https://git.openjdk.java.net/jmc/pull/344.diff
  Fetch: git fetch https://git.openjdk.java.net/jmc pull/344/head:pull/344

PR: https://git.openjdk.java.net/jmc/pull/344