This fixes issues with Alerts when the owner stage is not a valid stage with a scene and currently showing
------------- Commit messages: - Check owner stage for dialogs Changes: https://git.openjdk.org/jfx/pull/2127/files Webrev: https://webrevs.openjdk.org/?repo=jfx&pr=2127&range=00 Issue: https://bugs.openjdk.org/browse/JDK-8380926 Stats: 15 lines in 2 files changed: 8 ins; 2 del; 5 mod Patch: https://git.openjdk.org/jfx/pull/2127.diff Fetch: git fetch https://git.openjdk.org/jfx.git pull/2127/head:pull/2127 PR: https://git.openjdk.org/jfx/pull/2127
