[11] Request approval to backport 8211304: [macOS] Crash on focus loss from dialog on macOS 10.14 Mojave

[Kevin Rushforth]

Hi Johan,

I request approval to backport the following critical bug to 11-dev (for 
11.0.2).

JBS: https://bugs.openjdk.java.net/browse/JDK-8211304
Changeset: http://hg.openjdk.java.net/openjfx/jfx-dev/rt/rev/e864311d97e6

The changeset patch applies cleanly to 11-dev.

-- Kevin