Bug 92777 [Contributions] Spec clarification: ContributionItem.getParent() can return null
bundles/org.eclipse.jface/src/org/eclipse/jface/action/ContributionItem.java
/**
     * The identifier for this contribution item, of <code>null</code> if none.
     */
    private String id = null;
    /**
     * Indicates this item is visible in its manager; <code>true</code> 
     * by default.
     */
    private boolean visible = true;
    /**
     * The parent contribution manager for this item
     */
    private IContributionManager parent;
    /**
     * Creates a contribution item with a <code>null</code> id.
     * Calls <code>this(String)</code> with <code>null</code>.