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
fTree.setGrayed(element, true);
					return;
				}
				boolean state= event.getChecked();		
				fTree.setGrayed(element, false);
				if (isExpandable(element))
					setSubtreeChecked(element, state, state); 
					
				updateParentState(element, state);
				validateInput();
			}
		});
	}
	private void setSubtreeChecked(Object parent, boolean state, boolean checkExpandedState) {
		if (!(parent instanceof IAdaptable))
			return;
		IContainer container= (IContainer)((IAdaptable)parent).getAdapter(IContainer.class);
		if ((!fTree.getExpandedState(parent) && checkExpandedState) || (container != null && !container.isAccessible()))
			return;
		
		Object[] children= fTreeContentProvider.getChildren(parent);
		for (int i= children.length - 1; i >= 0; i--) {
			Object element= children[i];
			if (state) {
				fTree.setChecked(element, true);
				fTree.setGrayed(element, false);
			}
			else
				fTree.setGrayChecked(element, false);
			if (isExpandable(element))