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
* <p>
 * Working set elements are presented as a Java element tree.
 * </p>
 * 
 * @since 2.0
 */
public class JavaWorkingSetPage extends WizardPage implements IWorkingSetPage {
	final private static String PAGE_TITLE= WorkingSetMessages.getString("JavaWorkingSetPage.title"); 
	final private static String PAGE_ID= "javaWorkingSetPage"; 
	
	private Text fWorkingSetName;
	private CheckboxTreeViewer fTree;
	private ITreeContentProvider fTreeContentProvider;
	
	private boolean fFirstCheck;
	private IWorkingSet fWorkingSet;
	/**
	 * Default constructor.
	 */
	public JavaWorkingSetPage() {
		super(PAGE_ID, PAGE_TITLE, JavaPluginImages.DESC_WIZBAN_JAVA_WORKINGSET);
		setDescription(WorkingSetMessages.getString("JavaWorkingSetPage.workingSet.description")); 
		fFirstCheck= true;
	}
	/*
	 * @see org.eclipse.jface.dialogs.IDialogPage#createControl(org.eclipse.swt.widgets.Composite)
	 */
	public void createControl(Composite parent) {
		initializeDialogUnits(parent);