A trivial bugfix in `ListenerHelper`. --------- - [x] I confirm that I make this contribution in accordance with the [OpenJDK Interim AI Policy](https://openjdk.org/legal/ai).
------------- Commit messages: - the fix Changes: https://git.openjdk.org/jfx/pull/2345/files Webrev: https://webrevs.openjdk.org/?repo=jfx&pr=2345&range=00 Issue: https://bugs.openjdk.org/browse/JDK-8384258 Stats: 6 lines in 2 files changed: 4 ins; 0 del; 2 mod Patch: https://git.openjdk.org/jfx/pull/2345.diff Fetch: git fetch https://git.openjdk.org/jfx.git pull/2345/head:pull/2345 PR: https://git.openjdk.org/jfx/pull/2345
