NPE for junction checking

[stoecker]

What steps will reproduce the problem?

1. Open JOSM with plugin enabled
2. STRG-N for a new layer
3. Close JOSM

What is the expected result?
No crash

What happens instead?
A NPE probably caused by illegal checks in closing the software

Please provide any additional information below. Attach a screenshot if
possible.

Build-Date: 2011-02-04 21:09:34
Revision: 3853
Is-Local-Build: true

Identification: JOSM/1.5 (3853 SVN de)
Memory Usage: 87 MB / 455 MB (51 MB allocated, but free)
Java version: 1.6.0_23, Sun Microsystems Inc., Java HotSpot(TM) Server VM
Operating system: Linux

Plugin: buildings_tools (25192)
Plugin: editgpx (25192)
Plugin: junctionchecking (75)
Plugin: livegps (25192)
Plugin: turnrestrictions (25199)
Plugin: undelete (25199)

java.lang.NullPointerException
	at org.openstreetmap.josm.plugins.JunctionChecker.JunctionCheckerPlugin.activeLayerChange(JunctionCheckerPlugin.java:83)
	at org.openstreetmap.josm.gui.MapView.fireActiveLayerChanged(MapView.java:140)
	at org.openstreetmap.josm.gui.MapView.setActiveLayer(MapView.java:718)
	at org.openstreetmap.josm.gui.MapView.removeLayer(MapView.java:357)
	at org.openstreetmap.josm.Main.exitJosm(Main.java:538)
	at org.openstreetmap.josm.gui.MainApplication$1.windowClosing(MainApplication.java:65)
	at java.awt.AWTEventMulticaster.windowClosing(AWTEventMulticaster.java:332)
	at java.awt.AWTEventMulticaster.windowClosing(AWTEventMulticaster.java:332)
	at java.awt.AWTEventMulticaster.windowClosing(AWTEventMulticaster.java:332)
	at java.awt.Window.processWindowEvent(Window.java:1865)
	at javax.swing.JFrame.processWindowEvent(JFrame.java:274)
	at java.awt.Window.processEvent(Window.java:1823)
	at java.awt.Component.dispatchEventImpl(Component.java:4630)
	at java.awt.Container.dispatchEventImpl(Container.java:2099)
	at java.awt.Window.dispatchEventImpl(Window.java:2478)
	at java.awt.Component.dispatchEvent(Component.java:4460)
	at java.awt.EventQueue.dispatchEvent(EventQueue.java:599)
	at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:269)
	at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:184)
	at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:174)
	at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:169)
	at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:161)
	at java.awt.EventDispatchThread.run(EventDispatchThread.java:122)