[8u20] Review request for RT-16923: The various addListener methods should throw NPE if a null listener is passed in, rather than throwing NPE when the listener list is iterated

[Vadim Pakhnushev]

Hi Felipe, Anthony,

Please review this fix:
https://javafx-jira.kenai.com/browse/RT-16923
http://cr.openjdk.java.net/~vadim/RT-16923/webrev.00/

Thanks,
Vadim