Bug 287103 [CommonNavigator] contentServiceLabelProvider doesn't properly implement overrides
bundles/org.eclipse.ui.navigator/src/org/eclipse/ui/internal/navigator/extensions/NavigatorContentDescriptor.java
.getNamespaceIdentifier() }));
		}
		IConfigurationElement[] children = configElement
				.getChildren(TAG_ENABLEMENT);
		if (children.length == 0) {
			children = configElement.getChildren(TAG_TRIGGER_POINTS);
			if (children.length == 1) {
				enablement = new CustomAndExpression(children[0]);
			} else {
				throw new WorkbenchException(NLS.bind(
						CommonNavigatorMessages.Attribute_Missing_Warning,
						new Object[] {
								TAG_TRIGGER_POINTS,
								id,
								configElement.getDeclaringExtension()
										.getNamespaceIdentifier() }));
			}
			children = configElement.getChildren(TAG_POSSIBLE_CHILDREN);
			if (children.length == 1) {
				possibleChildren = new CustomAndExpression(children[0]);
			} else if(children.length > 1){
				throw new WorkbenchException(NLS.bind(
						CommonNavigatorMessages.Attribute_Missing_Warning,
						new Object[] {
								TAG_POSSIBLE_CHILDREN,
								id,
								configElement.getDeclaringExtension()
										.getNamespaceIdentifier() }));
			}
		} else if (children.length == 1) {