Bug 311396 NPE thrown when trying to close a part that hasn't been restored
An NPE is thrown because we try to ask the part for a context. However, if the part hasn't been rendered yet, we'll get null back. java.lang.NullPointerException at org.eclipse.e4.workbench.ui.renderers.swt.StackRenderer$6.close(StackRenderer.java:449) at org.eclipse.swt.custom.CTabFolder.onMouse(CTabFolder.java:1590) at org.eclipse.swt.custom.CTabFolder$1.handleEvent(CTabFolder.java:261) at org.eclipse.swt.widgets.EventTable.sendEvent(EventTable.java:84) at org.eclipse.swt.widgets.Widget.sendEvent(Widget.java:1052) at org.eclipse.swt.widgets.Display.runDeferredEvents(Display.java:4066) at org.eclipse.swt.widgets.Display.readAndDispatch(Display.java:3657) at org.eclipse.e4.ui.workbench.swt.internal.PartRenderingEngine$4.run(PartRenderingEngine.java:517) at org.eclipse.core.databinding.observable.Realm.runWithDefault(Realm.java:332) at org.eclipse.e4.ui.workbench.swt.internal.PartRenderingEngine.run(PartRenderingEngine.java:455) at org.eclipse.e4.workbench.ui.internal.E4Workbench.createAndRunUI(E4Workbench.java:100) at org.eclipse.ui.internal.Workbench$3.run(Workbench.java:533) at org.eclipse.core.databinding.observable.Realm.runWithDefault(Realm.java:332) at org.eclipse.ui.internal.Workbench.createAndRunWorkbench(Workbench.java:519) 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(NativeMethodAccessorImpl.java:48) at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:37) at java.lang.reflect.Method.invoke(Method.java:600) 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) at org.eclipse.equinox.launcher.Main.main(Main.java:1383)
bundles/org.eclipse.e4.ui.workbench.renderers.swt/src/org/eclipse/e4/workbench/ui/renderers/swt/StackRenderer.java
trackingContext.get(FOLDER_DISPOSED);
				IEclipseContext currentActive = toplevelContext;
				IEclipseContext child;
				while (currentActive != trackingContext
						&& (child = (IEclipseContext) currentActive
								.get("activeChild")) != null && child != currentActive) { 
					currentActive = child;
				}
				
				String cssClassName = (currentActive == trackingContext) ? "active" 
						: "inactive"; 
				stylingEngine.setClassname(ctf, cssClassName);
				
				
				if (ctf.getTopRight() != null)
					stylingEngine.setClassname(ctf.getTopRight(), cssClassName);
				
				
				CTabItem[] items = ctf.getItems();
				for (int i = 0; i < items.length; i++) {
					stylingEngine.setClassname(items[i], cssClassName);
				}
				return true;
			}
		};
		ctf.addDisposeListener(new DisposeListener() {
			public void widgetDisposed(DisposeEvent e) {
				updateActiveTab.participating = false;
				folderContext.set(FOLDER_DISPOSED, Boolean.TRUE);
			}