Fix NullPointerException in TrackWidget when scrolling

[Fabian Rohn]

Reconstruction:

• do not scroll by holding the mousbutton but click as fast as possible on the green border for scrolling

java.lang.NullPointerException
de.jacavi.rcp.widgets.TrackWidget.adjustPanPositionBounded(TrackWidget.java:685)
de.jacavi.rcp.widgets.TrackWidget.handleInnerControlClick(TrackWidget.java:521)
de.jacavi.rcp.widgets.TrackWidget.handleMouseDown(TrackWidget.java:479)
de.jacavi.rcp.widgets.TrackWidget$1.mouseDown(TrackWidget.java:337)
org.eclipse.swt.widgets.TypedListener.handleEvent(TypedListener.java:178)
org.eclipse.swt.widgets.EventTable.sendEvent(EventTable.java:84)
org.eclipse.swt.widgets.Widget.sendEvent(Widget.java:1002)
org.eclipse.swt.widgets.Display.runDeferredEvents(Display.java:3782)
org.eclipse.swt.widgets.Display.readAndDispatch(Display.java:3381)
org.eclipse.ui.internal.Workbench.runEventLoop(Workbench.java:2394)
org.eclipse.ui.internal.Workbench.runUI(Workbench.java:2358)
org.eclipse.ui.internal.Workbench.access$4(Workbench.java:2210)
org.eclipse.ui.internal.Workbench$5.run(Workbench.java:494)
org.eclipse.core.databinding.observable.Realm.runWithDefault(Realm.java:288)
org.eclipse.ui.internal.Workbench.createAndRunWorkbench(Workbench.java:489)
org.eclipse.ui.PlatformUI.createAndRunWorkbench(PlatformUI.java:149)
de.jacavi.rcp.Application.start(Application.java:25)
org.eclipse.equinox.internal.app.EclipseAppHandle.run(EclipseAppHandle.java:193)
org.eclipse.core.runtime.internal.adaptor.EclipseAppLauncher.runApplication(EclipseAppLauncher.java:110)
org.eclipse.core.runtime.internal.adaptor.EclipseAppLauncher.start(EclipseAppLauncher.java:79)
org.eclipse.core.runtime.adaptor.EclipseStarter.run(EclipseStarter.java:379)
org.eclipse.core.runtime.adaptor.EclipseStarter.run(EclipseStarter.java:179)
sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
java.lang.reflect.Method.invoke(Method.java:597)
org.eclipse.equinox.launcher.Main.invokeFramework(Main.java:549)
org.eclipse.equinox.launcher.Main.basicRun(Main.java:504)
org.eclipse.equinox.launcher.Main.run(Main.java:1236)
org.eclipse.equinox.launcher.Main.main(Main.java:1212)

[SVN]

New commit by hheimbuerger (revision [393]):
[Fix for ticket #135] Added naive fix for NullPointerException.

No longer preliminarily setting the lastTrackBoundingBox to null because it might be needed by input handling code before the next redraw.

[Henrik Heimbuerger]

Assigned back for testing.