<AWT Dev> [8] Please review fix for 7175704: [macosx] "8" PIT: NPE in GetDisplayMode fullscreen test

[Alexander Zuev]

Hello,

   please review my fix for CR 7175704: [macosx] "8" PIT: NPE in 
GetDisplayMode fullscreen test

   The NPE happens because we do not check the passed argument to null 
before using it. The correct exception according to the specification 
should be IllegalArgumentException.

Bug description is: 
http://bugs.sun.com/bugdatabase/view_bug.do?bug_id=7175704
Webrev can be found here: 
http://cr.openjdk.java.net/~kizune/7175704/webrev.00

With best regards,
Alex