JavaFX bug? Crashes stage

Question

I have a string that is built up of 2 dynamically updated fields. For some reason, this seems tricky and poorly supported.
public var heading: Number = DEFAULT_HEADING;
public var fid: Number = 0 ;
var labelString = bind "fid: {%.0f fid} angle: {%.0f 360*(heading/(2*PI))}";;
//var labelString = "";
//public var fid: Number = 0 on replace{
// labelString = "fid: {%.0f fid} angle: {%.0f 360*(heading/(2*PI))}";
labelString is used by a text node for its content via bind. The commented out version only ever updates once, no further ones are processed.
Is there a better way to build a dynamically updating string?
This is part of a custom node, and when fid and heading are modified, the heading indicator on my node updates fine. But after a second, the stage stops updating the display after the following exception is displayed:
Unexpected exception caught in MasterTimer.timePulse():
java.lang.NullPointerException
at com.sun.scenario.scenegraph.SGText.getRawBounds(SGText.java:1129)
at com.sun.scenario.scenegraph.SGText.getBounds(SGText.java:1003)
at com.sun.scenario.scenegraph.SGNode.calculateAccumBounds(SGNode.java:316)
at com.sun.scenario.scenegraph.SGNode.getTransformedBounds(SGNode.java:302)
at com.sun.scenario.scenegraph.SGNode.accumulateDirty(SGNode.java:902)
at com.sun.scenario.scenegraph.SGWrapper.accumulateDirtyChildren(SGWrapper.java:106)
at com.sun.scenario.scenegraph.SGNode.accumulateDirty(SGNode.java:904)
at com.sun.scenario.scenegraph.SGGroup.accumulateDirtyChildren(SGGroup.java:282)
at com.sun.scenario.scenegraph.SGNode.accumulateDirty(SGNode.java:904)
at com.sun.scenario.scenegraph.SGWrapper.accumulateDirtyChildren(SGWrapper.java:106)
at com.sun.scenario.scenegraph.SGNode.accumulateDirty(SGNode.java:904)
at com.sun.scenario.scenegraph.SGGroup.accumulateDirtyChildren(SGGroup.java:282)
at com.sun.scenario.scenegraph.SGNode.accumulateDirty(SGNode.java:904)
at com.sun.scenario.scenegraph.SGWrapper.accumulateDirtyChildren(SGWrapper.java:106)
at com.sun.scenario.scenegraph.SGNode.accumulateDirty(SGNode.java:904)
at com.sun.scenario.scenegraph.SGGroup.accumulateDirtyChildren(SGGroup.java:282)
at com.sun.scenario.scenegraph.SGNode.accumulateDirty(SGNode.java:904)
at com.sun.scenario.scenegraph.SGGroup.accumulateDirtyChildren(SGGroup.java:282)
at com.sun.scenario.scenegraph.SGNode.accumulateDirty(SGNode.java:904)
at com.sun.scenario.scenegraph.JSGPanel.accumulateDirtyRegions(JSGPanel.java:763)
at com.sun.scenario.scenegraph.JSGPanel.repaintDirtyRegions(JSGPanel.java:611)
at com.sun.scenario.scenegraph.JSGPanelRepainter.repaintAll(JSGPanelRepainter.java:106)
at com.sun.scenario.scenegraph.JSGPanelRepainter$FrameDisplay.run(JSGPanelRepainter.java:112)
at com.sun.scenario.animation.AbstractMasterTimer.timePulseImpl(AbstractMasterTimer.java:365)
at com.sun.scenario.animation.AbstractMasterTimer$MainLoop.run(AbstractMasterTimer.java:247)
at com.sun.embeddedswing.EmbeddedEventQueue.doPulse(EmbeddedEventQueue.java:470)
at com.sun.embeddedswing.EmbeddedEventQueue.access$000(EmbeddedEventQueue.java:72)
at com.sun.embeddedswing.EmbeddedEventQueue$2.run(EmbeddedEventQueue.java:377)
at java.awt.event.InvocationEvent.dispatch(Unknown Source)
at java.awt.EventQueue.dispatchEvent(Unknown Source)
at java.awt.EventDispatchThread.pumpOneEventForFilters(Unknown Source)
at java.awt.EventDispatchThread.pumpEventsForFilter(Unknown Source)
at java.awt.EventDispatchThread.pumpEventsForHierarchy(Unknown Source)
at java.awt.EventDispatchThread.pumpEvents(Unknown Source)
at java.awt.EventDispatchThread.pumpEvents(Unknown Source)
at java.awt.EventDispatchThread.run(Unknown Source)
I can't seem where to file a bug.

Answer 1

I can't guarantee that I am correct here, but dees your bind "fid: {%.0f fid} angle: {%.0f 360*(heading/(2*PI))}"; ever return null? and if so... what ever is bound to labelString can it cope with labelString being null?
Maybe take a look at the 'on replace' functionality, and see if you can provide some pre/post condition checking to prevent the propogation of null vales throughout your bind references.
Also, I still find set() operations good practice when you can write to something opposed to directly writing to the var. There is a reason why this is NOT done on java classes and that reason is exactly the same in JavaFX :)
If you really want a solution, checkout how to use the netbeans debugger... you'll soon see what's null when.