FProxy: add JVM End of Life useralert
FProxy: avoid version check NPE on null "system.version" property

In its current usage this will prevent the version alert from displaying
as well. This is good because if an HTMLNode is given a null attribute
value it will throw IllegalArgumentException, and because the alert is an
error it is displayed on all FProxy pages.
Merge remote-tracking branch 'origin/version-warning' into next