org.drools.eclipse.core.DefaultRuleGroup cannot be cast to org.eclipse.emf.ecore.EObject

1) Drools workbench -> New drools project -> any proj name -> check all checkboxes -> other by default;
2) open Sample.drl;
3) in Outline view -> click on nodes -> click on default -> get exception:

org.drools.eclipse.core.DefaultRuleGroup cannot be cast to org.eclipse.emf.ecore.EObject

java.lang.ClassCastException: org.drools.eclipse.core.DefaultRuleGroup cannot be cast to org.eclipse.emf.ecore.EObject
at com.metamatrix.modeler.internal.ui.actions.workers.ModelObjectWorker.isReadOnly(ModelObjectWorker.java:134)
at com.metamatrix.modeler.internal.ui.actions.workers.CloneWorker.setEnabledState(CloneWorker.java:58)
at com.metamatrix.modeler.internal.ui.actions.workers.ModelObjectWorker.selectionChanged(ModelObjectWorker.java:181)
at com.metamatrix.modeler.internal.ui.actions.DesignerUiPropertyTester.isCloneAllowed(DesignerUiPropertyTester.java:91)
at com.metamatrix.modeler.internal.ui.actions.DesignerUiPropertyTester.test(DesignerUiPropertyTester.java:45)
at org.eclipse.core.internal.expressions.Property.test(Property.java:58)
at org.eclipse.core.internal.expressions.TestExpression.evaluate(TestExpression.java:99)
at org.eclipse.ui.internal.services.EvaluationResultCache.evaluate(EvaluationResultCache.java:74)
at org.eclipse.ui.internal.services.ExpressionAuthority.evaluate(ExpressionAuthority.java:165)
at org.eclipse.ui.internal.services.EvaluationAuthority.refsWithSameExpression(EvaluationAuthority.java:155)
at org.eclipse.ui.internal.services.EvaluationAuthority.sourceChanged(EvaluationAuthority.java:129)
at org.eclipse.ui.internal.services.ExpressionAuthority.sourceChanged(ExpressionAuthority.java:311)
at org.eclipse.ui.internal.services.ExpressionAuthority.sourceChanged(ExpressionAuthority.java:302)
at org.eclipse.ui.AbstractSourceProvider.fireSourceChanged(AbstractSourceProvider.java:80)
at org.eclipse.ui.internal.services.WorkbenchSourceProvider.selectionChanged(WorkbenchSourceProvider.java:177)
at org.eclipse.ui.internal.AbstractSelectionService.fireSelection(AbstractSelectionService.java:156)
at org.eclipse.ui.internal.AbstractSelectionService$1.selectionChanged(AbstractSelectionService.java:62)
at org.eclipse.ui.part.PageBookView$5.run(PageBookView.java:255)
at org.eclipse.core.runtime.SafeRunner.run(SafeRunner.java:42)
at org.eclipse.core.runtime.Platform.run(Platform.java:888)
at org.eclipse.ui.part.PageBookView$SelectionManager.selectionChanged(PageBookView.java:253)
at org.eclipse.ui.part.PageBookView$SelectionProvider.selectionChanged(PageBookView.java:319)
at org.eclipse.ui.part.PageBookView.pageSelectionChanged(PageBookView.java:896)
at org.eclipse.ui.part.PageBookView.access$2(PageBookView.java:891)
at org.eclipse.ui.part.PageBookView$2.selectionChanged(PageBookView.java:163)
at org.eclipse.ui.views.contentoutline.ContentOutlinePage$1.run(ContentOutlinePage.java:99)
at org.eclipse.core.runtime.SafeRunner.run(SafeRunner.java:42)
at org.eclipse.ui.views.contentoutline.ContentOutlinePage.fireSelectionChanged(ContentOutlinePage.java:97)
at org.eclipse.ui.views.contentoutline.ContentOutlinePage.selectionChanged(ContentOutlinePage.java:157)
at org.eclipse.jface.viewers.Viewer$2.run(Viewer.java:162)
at org.eclipse.core.runtime.SafeRunner.run(SafeRunner.java:42)
at org.eclipse.ui.internal.JFaceUtil$1.run(JFaceUtil.java:49)
at org.eclipse.jface.util.SafeRunnable.run(SafeRunnable.java:175)
at org.eclipse.jface.viewers.Viewer.fireSelectionChanged(Viewer.java:160)
at org.eclipse.jface.viewers.StructuredViewer.updateSelection(StructuredViewer.java:2162)
at org.eclipse.jface.viewers.StructuredViewer.handleSelect(StructuredViewer.java:1190)
at org.eclipse.jface.viewers.StructuredViewer$4.widgetSelected(StructuredViewer.java:1220)
at org.eclipse.jface.util.OpenStrategy.fireSelectionEvent(OpenStrategy.java:228)
at org.eclipse.jface.util.OpenStrategy.access$4(OpenStrategy.java:222)
at org.eclipse.jface.util.OpenStrategy$1.handleEvent(OpenStrategy.java:389)
at org.eclipse.swt.widgets.EventTable.sendEvent(EventTable.java:84)
at org.eclipse.swt.widgets.Widget.sendEvent(Widget.java:1053)
at org.eclipse.swt.widgets.Display.runDeferredEvents(Display.java:4066)
at org.eclipse.swt.widgets.Display.readAndDispatch(Display.java:3657)
at org.eclipse.ui.internal.Workbench.runEventLoop(Workbench.java:2640)
at org.eclipse.ui.internal.Workbench.runUI(Workbench.java:2604)
at org.eclipse.ui.internal.Workbench.access$4(Workbench.java:2438)
at org.eclipse.ui.internal.Workbench$7.run(Workbench.java:671)
at org.eclipse.core.databinding.observable.Realm.runWithDefault(Realm.java:332)
at org.eclipse.ui.internal.Workbench.createAndRunWorkbench(Workbench.java:664)
at org.eclipse.ui.PlatformUI.createAndRunWorkbench(PlatformUI.java:149)
at org.eclipse.ui.internal.ide.application.IDEApplication.start(IDEApplication.java:115)
at org.eclipse.equinox.internal.app.EclipseAppHandle.run(EclipseAppHandle.java:196)
at org.eclipse.core.runtime.internal.adaptor.EclipseAppLauncher.runApplication(EclipseAppLauncher.java:110)
at org.eclipse.core.runtime.internal.adaptor.EclipseAppLauncher.start(EclipseAppLauncher.java:79)
at org.eclipse.core.runtime.adaptor.EclipseStarter.run(EclipseStarter.java:369)
at org.eclipse.core.runtime.adaptor.EclipseStarter.run(EclipseStarter.java:179)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
at java.lang.reflect.Method.invoke(Unknown Source)
at org.eclipse.equinox.launcher.Main.invokeFramework(Main.java:619)
at org.eclipse.equinox.launcher.Main.basicRun(Main.java:574)
at org.eclipse.equinox.launcher.Main.run(Main.java:1407)