Bug 296253 [CommonNavigator] An empty label is not properly shown when it is the only contributed label
tests/org.eclipse.ui.tests.navigator/src/org/eclipse/ui/tests/navigator/LabelProviderTest.java
public LabelProviderTest() {
		_navigatorInstanceId = "org.eclipse.ui.tests.navigator.OverrideTestView";
	}
	private static final boolean BLANK = true;
	private static final boolean NULL = false;
	
	private static final String PLAIN = "Plain";
	
	
	public void blankLabelProviderOverride(boolean blank, String suffix) throws Exception {
		
		String overriddenCp = TEST_CONTENT_OVERRIDDEN1 + suffix;
		String overrideCp = TEST_CONTENT_OVERRIDE1 + suffix;
		
		
		NavigatorContentExtension ext = (NavigatorContentExtension) _contentService.getContentExtensionById(overrideCp);
		TestLabelProvider tp = (TestLabelProvider) ext.getLabelProvider();
		if (blank)
			tp._blank = true;
		else 
			tp._null = true;
		
		_contentService.bindExtensions(new String[] { overriddenCp, overrideCp }, false);
		_contentService.getActivationService()
				.activateExtensions(
						new String[] { overrideCp, overriddenCp }, true);
		refreshViewer();