Clean backport of adding simple null checks in glass screen fix to the `jfx25` stabilization branch.
------------- Commit messages: - Backport dbd43a371a2460c3cf8aed108d349b301bd2a1b2 Changes: https://git.openjdk.org/jfx/pull/1854/files Webrev: https://webrevs.openjdk.org/?repo=jfx&pr=1854&range=00 Issue: https://bugs.openjdk.org/browse/JDK-8363813 Stats: 31 lines in 4 files changed: 10 ins; 4 del; 17 mod Patch: https://git.openjdk.org/jfx/pull/1854.diff Fetch: git fetch https://git.openjdk.org/jfx.git pull/1854/head:pull/1854 PR: https://git.openjdk.org/jfx/pull/1854
