[LineChart] NPE when updating LineChart data

Regression starting with 8u20 build 07.

The following NPE is thrown when updating a LineChart series on a timer, using RunLater. This only happens if createSymbols is false.

java.lang.NullPointerException: Children: child node is null: parent = Group@6e60fd98[styleClass=plot-content]
at javafx.scene.Parent$2.onProposedChange(Parent.java:431)
at com.sun.javafx.collections.VetoableListDecorator.add(VetoableListDecorator.java:206)
at javafx.scene.chart.LineChart.lambda$dataItemAdded$535(LineChart.java:242)
at javafx.scene.chart.LineChart$$Lambda$124/883866724.handle(Unknown Source)
at com.sun.scenario.animation.shared.TimelineClipCore.visitKeyFrame(TimelineClipCore.java:226)
at com.sun.scenario.animation.shared.TimelineClipCore.playTo(TimelineClipCore.java:167)
at javafx.animation.Timeline.impl_playTo(Timeline.java:161)
at javafx.animation.AnimationAccessorImpl.playTo(AnimationAccessorImpl.java:39)
at com.sun.scenario.animation.shared.SingleLoopClipEnvelope.timePulse(SingleLoopClipEnvelope.java:99)
at javafx.animation.Animation.impl_timePulse(Animation.java:1102)
at javafx.animation.Animation$1.lambda$timePulse$26(Animation.java:186)
at javafx.animation.Animation$1$$Lambda$114/528365738.run(Unknown Source)
at java.security.AccessController.doPrivileged(Native Method)
at javafx.animation.Animation$1.timePulse(Animation.java:185)
at com.sun.scenario.animation.AbstractMasterTimer.timePulseImpl(AbstractMasterTimer.java:344)
at com.sun.scenario.animation.AbstractMasterTimer$MainLoop.run(AbstractMasterTimer.java:267)
at com.sun.javafx.tk.quantum.QuantumToolkit.pulse(QuantumToolkit.java:440)
at com.sun.javafx.tk.quantum.QuantumToolkit.pulse(QuantumToolkit.java:424)
at com.sun.javafx.tk.quantum.QuantumToolkit.lambda$runToolkit$350(QuantumToolkit.java:295)
at com.sun.javafx.tk.quantum.QuantumToolkit$$Lambda$46/440631373.run(Unknown Source)
at com.sun.glass.ui.InvokeLaterDispatcher$Future.run(InvokeLaterDispatcher.java:95)
at com.sun.glass.ui.gtk.GtkApplication._runLoop(Native Method)
at com.sun.glass.ui.gtk.GtkApplication.lambda$null$46(GtkApplication.java:126)
at com.sun.glass.ui.gtk.GtkApplication$$Lambda$42/183264084.run(Unknown Source)
at java.lang.Thread.run(Thread.java:744)