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
if (items[i].getChecked())
				return true;
		}
		return false;
	}
	
	private void disableClosedProjects() {
		IProject[] projects= ResourcesPlugin.getWorkspace().getRoot().getProjects();
		for (int i= 0; i < projects.length; i++) {
			if (!projects[i].isOpen())
				fTree.setGrayed(projects[i], true);
		}
	}
	private void findCheckedElements(List checkedResources, Object parent) {
		Object[] children= fTreeContentProvider.getChildren(parent);
		for (int i= 0; i < children.length; i++) {
			if (fTree.getGrayed(children[i]))
				findCheckedElements(checkedResources, children[i]);
			else if (fTree.getChecked(children[i]))
				checkedResources.add(children[i]);
		}
	}
	void handleCheckStateChange(final CheckStateChangedEvent event) {
		BusyIndicator.showWhile(getShell().getDisplay(), new Runnable() {
			public void run() {
				IAdaptable element= (IAdaptable)event.getElement();
				IResource resource= (IResource)element.getAdapter(IResource.class);
				if (resource != null && !resource.isAccessible()) {
					MessageDialog.openInformation(getShell(), WorkingSetMessages.getString("JavaWorkingSetPage.projectClosedDialog.title"), WorkingSetMessages.getString("JavaWorkingSetPage.projectClosedDialog.message")); 
					fTree.setChecked(element, false);