hg: openjfx/8/controls/rt: fix RT-26820 ChoiceBox with no items throws exception when added to live scene.

[hang.vo at oracle.com]

Changeset: a867b54962e3
Author:    Paru Somashekar <paru.somashekar at oracle.com>
Date:      2012-12-10 11:57 -0800
URL:       http://hg.openjdk.java.net/openjfx/8/controls/rt/rev/a867b54962e3

fix RT-26820 ChoiceBox with no items throws exception when added to live scene.
+ unit test.

! javafx-ui-controls/src/com/sun/javafx/scene/control/skin/ContextMenuContent.java
! javafx-ui-controls/test/javafx/scene/control/ChoiceBoxTest.java