<AWT Dev> [7u10] Please review fix for 7175183: [macosx] Objective-C exception thrown when switching monitor configuration

[Alexander Zuev]

Hello,

   please review my fix for CR 7175183: [macosx] Objective-C exception 
thrown when switching monitor configuration

   This is a backport of the fix already pushed into jdk8. Fix is 
absolutely the same i just need reviewers to formally ask for an 
approval to push it to jdk7u10.

Bug description is: 
http://bugs.sun.com/bugdatabase/view_bug.do?bug_id=7175183
Webrev can be found here: 
http://cr.openjdk.java.net/~kizune/7175183/webrev.01

With best regards,
Alex