Bug 127746 [build path] Build Path action "no actions available" should be disabled
org.eclipse.jdt.ui/ui/org/eclipse/jdt/internal/ui/wizards/buildpaths/newsourcepage/GenerateBuildPathActionGroup.java
private boolean canOperateOnSelection() {
    	ISelection sel= fSite.getSelectionProvider().getSelection();
    	if (!(sel instanceof IStructuredSelection))
    		return false;
    	IStructuredSelection selection= (IStructuredSelection)sel;
    	for (Iterator iter= selection.iterator(); iter.hasNext();) {
			Object element= iter.next();
			if (element instanceof IWorkingSet)
				return false;
		}
    	return true;
    }
	/**
	 * {@inheritDoc}
	 */
	public void dispose() {
		if (fActions != null) {
			final ISelectionProvider provider= fSite.getSelectionProvider();
			for (int index= 0; index < fActions.length; index++) {
				final IAction action= fActions[index];
				if (action instanceof ISelectionChangedListener)
					provider.removeSelectionChangedListener((ISelectionChangedListener) action);
			}
		}
		fActions= null;
		super.dispose();
	}
}