Bug 39027 [working sets] Edit active working set prevents removal of closed projects.
When editing the "active working set" closed projects cannot be removed from the working set, the project has to be opened so it can be removed. This is a minor usability issue.
org.eclipse.jdt.ui/ui/org/eclipse/jdt/internal/ui/workingsets/JavaWorkingSetPage.java
AppearanceAwareLabelProvider fJavaElementLabelProvider= 
			new AppearanceAwareLabelProvider(
				AppearanceAwareLabelProvider.DEFAULT_TEXTFLAGS | JavaElementLabels.P_COMPRESSED,
				AppearanceAwareLabelProvider.DEFAULT_IMAGEFLAGS | JavaElementImageProvider.SMALL_ICONS
			);
		
		fTree.setLabelProvider(new DecoratingJavaLabelProvider(fJavaElementLabelProvider));
		fTree.setSorter(new JavaElementSorter());
		fTree.addFilter(new EmptyInnerPackageFilter());
		fTree.setUseHashlookup(true);
		
		fTree.setInput(JavaCore.create(ResourcesPlugin.getWorkspace().getRoot()));
		fTree.addCheckStateListener(new ICheckStateListener() {
			public void checkStateChanged(CheckStateChangedEvent event) {
				handleCheckStateChange(event);
			}
		});
		fTree.addTreeListener(new ITreeViewerListener() {
			public void treeCollapsed(TreeExpansionEvent event) {
			}
			public void treeExpanded(TreeExpansionEvent event) {
				final Object element= event.getElement();
				if (fTree.getGrayed(element) == false)
					BusyIndicator.showWhile(getShell().getDisplay(), new Runnable() {
					public void run() {
						setSubtreeChecked(element, fTree.getChecked(element), false);
					}
				});
			}