NPE when stopping automation core

[BenediktNiehues]

A NullPointerException occurs when automation bundle is stopped after test executions in eclipse.
In the stop method of the automation.core.Activator, serviceTracker.close is called, which results in a removedService call of the ServiceTrackerCustomizer. This uses the ruleRegistry, but it was already set to null in the stop method.

There has to be added a null-check for the ruleRegistry in ServiceTrackerCustomizer and the serviceTracker.close() should be called before the ruleRegistry is set to null...

StackTrace:
org.osgi.framework.BundleException: Exception in org.eclipse.smarthome.automation.core.internal.Activator.stop() of bundle org.eclipse.smarthome.automation.core.
at org.eclipse.osgi.internal.framework.BundleContextImpl.stop(BundleContextImpl.java:847)
at org.eclipse.osgi.internal.framework.EquinoxBundle.stopWorker0(EquinoxBundle.java:950)
at org.eclipse.osgi.internal.framework.EquinoxBundle$EquinoxModule.stopWorker(EquinoxBundle.java:324)
at org.eclipse.osgi.container.Module.doStop(Module.java:626)
at org.eclipse.osgi.container.Module.stop(Module.java:488)
at org.eclipse.osgi.container.ModuleContainer$ContainerStartLevel.decStartLevel(ModuleContainer.java:1623)
at org.eclipse.osgi.container.ModuleContainer$ContainerStartLevel.doContainerStartLevel(ModuleContainer.java:1542)
at org.eclipse.osgi.container.SystemModule.stopWorker(SystemModule.java:248)
at org.eclipse.osgi.internal.framework.EquinoxBundle$SystemBundle$EquinoxSystemModule.stopWorker(EquinoxBundle.java:145)
at org.eclipse.osgi.container.Module.doStop(Module.java:626)
at org.eclipse.osgi.container.Module.stop(Module.java:488)
at org.eclipse.osgi.container.SystemModule.stop(SystemModule.java:186)
at org.eclipse.osgi.internal.framework.EquinoxBundle$SystemBundle$EquinoxSystemModule$1.run(EquinoxBundle.java:160)
at java.lang.Thread.run(Thread.java:745)
Caused by: java.lang.NullPointerException
at org.eclipse.smarthome.automation.core.internal.Activator$1.removedService(Activator.java:139)
at org.osgi.util.tracker.ServiceTracker$Tracked.customizerRemoved(ServiceTracker.java:967)
at org.osgi.util.tracker.ServiceTracker$Tracked.customizerRemoved(ServiceTracker.java:1)
at org.osgi.util.tracker.AbstractTracked.untrack(AbstractTracked.java:341)
at org.osgi.util.tracker.ServiceTracker.close(ServiceTracker.java:377)
at org.eclipse.smarthome.automation.core.internal.Activator.stop(Activator.java:187)
at org.eclipse.osgi.internal.framework.BundleContextImpl$4.run(BundleContextImpl.java:827)
at org.eclipse.osgi.internal.framework.BundleContextImpl$4.run(BundleContextImpl.java:1)
at java.security.AccessController.doPrivileged(Native Method)
at org.eclipse.osgi.internal.framework.BundleContextImpl.stop(BundleContextImpl.java:820)
... 13 more
Root exception:
java.lang.NullPointerException
at org.eclipse.smarthome.automation.core.internal.Activator$1.removedService(Activator.java:139)
at org.osgi.util.tracker.ServiceTracker$Tracked.customizerRemoved(ServiceTracker.java:967)
at org.osgi.util.tracker.ServiceTracker$Tracked.customizerRemoved(ServiceTracker.java:1)
at org.osgi.util.tracker.AbstractTracked.untrack(AbstractTracked.java:341)
at org.osgi.util.tracker.ServiceTracker.close(ServiceTracker.java:377)
at org.eclipse.smarthome.automation.core.internal.Activator.stop(Activator.java:187)
at org.eclipse.osgi.internal.framework.BundleContextImpl$4.run(BundleContextImpl.java:827)
at org.eclipse.osgi.internal.framework.BundleContextImpl$4.run(BundleContextImpl.java:1)
at java.security.AccessController.doPrivileged(Native Method)
at org.eclipse.osgi.internal.framework.BundleContextImpl.stop(BundleContextImpl.java:820)
at org.eclipse.osgi.internal.framework.EquinoxBundle.stopWorker0(EquinoxBundle.java:950)
at org.eclipse.osgi.internal.framework.EquinoxBundle$EquinoxModule.stopWorker(EquinoxBundle.java:324)
at org.eclipse.osgi.container.Module.doStop(Module.java:626)
at org.eclipse.osgi.container.Module.stop(Module.java:488)
at org.eclipse.osgi.container.ModuleContainer$ContainerStartLevel.decStartLevel(ModuleContainer.java:1623)
at org.eclipse.osgi.container.ModuleContainer$ContainerStartLevel.doContainerStartLevel(ModuleContainer.java:1542)
at org.eclipse.osgi.container.SystemModule.stopWorker(SystemModule.java:248)
at org.eclipse.osgi.internal.framework.EquinoxBundle$SystemBundle$EquinoxSystemModule.stopWorker(EquinoxBundle.java:145)
at org.eclipse.osgi.container.Module.doStop(Module.java:626)
at org.eclipse.osgi.container.Module.stop(Module.java:488)
at org.eclipse.osgi.container.SystemModule.stop(SystemModule.java:186)
at org.eclipse.osgi.internal.framework.EquinoxBundle$SystemBundle$EquinoxSystemModule$1.run(EquinoxBundle.java:160)
at java.lang.Thread.run(Thread.java:745)