[10] Review request for 8172847 [macos] If you hit the escape key repeatedly to close the subwindow, the process crashes

[Alexander Zvegintsev]

Hello,

please review the fix
http://cr.openjdk.java.net/~azvegint/jdk/10/8172847/00/
for the issue
https://bugs.openjdk.java.net/browse/JDK-8172847

-- 
Thanks,
Alexander.