Bug 139511 [CommonNavigator] getParent() fails in certain cases
In the implementation of getParents(), clients can sometimes fail to return the correct parent with the override cases taken into account. The attached patch fixes these issues, but should be reviewed by the Team Team to ensure that it does not cause any regressions for their cases.
bundles/org.eclipse.ui.navigator/src/org/eclipse/ui/internal/navigator/extensions/NavigatorContentDescriptor.java
*             if an instance of the executable extension could not be
	 *             created for any reason
	 */
	public ILabelProvider createLabelProvider() throws CoreException {
		return (ILabelProvider) configElement
				.createExecutableExtension(ATT_LABEL_PROVIDER);
	}
	/*
	 * (non-Javadoc)
	 * 
	 * @see org.eclipse.ui.internal.navigator.extensions.INavigatorContentDescriptor#isEnabledByDefault()
	 */
	public boolean isActiveByDefault() {
		return activeByDefault;
	}
	/**
	 * Determine if this content extension would be able to provide children for
	 * the given element.
	 * 
	 * @param anElement
	 *            The element that should be used for the evaluation.
	 * @return True if and only if the extension is enabled for the element.
	 */
	public boolean isTriggerPoint(Object anElement) {
		if (enablement == null || anElement == null) {
			return false;
		}
		try {
			EvaluationContext context = new EvaluationContext(null, anElement);
			context.setAllowPluginActivation(true);