Bug 299208 [CommonNavigator] More helpful error message when an invalid suppressedExtensionId is referenced
The current error message does not show the if of the NCE that had the bad reference.
bundles/org.eclipse.ui.navigator/src/org/eclipse/ui/internal/navigator/extensions/NavigatorContentDescriptorManager.java
}
		return image;
	}
	/**
	 * @param desc
	 */
	private void addNavigatorContentDescriptor(NavigatorContentDescriptor desc) {
		if (desc == null) {
			return;
		}
		synchronized (firstClassDescriptorsMap) {
			if (firstClassDescriptorsMap.containsKey(desc.getId())) {
				NavigatorPlugin
						.logError(
								0,
								"An extension already exists with id \"" + desc.getId() + "\".", null); 
			} else {
				if (desc.getSuppressedExtensionId() == null) {
					firstClassDescriptorsMap.put(desc.getId(), desc);
					firstClassDescriptorsSet.add(desc);
					if (Policy.DEBUG_EXTENSION_SETUP) {
						System.out.println("First class descriptor: " + desc); 
					}
				} else {
					overridingDescriptors.add(desc);
					if (Policy.DEBUG_EXTENSION_SETUP) {
						System.out.println("Overriding descriptor: " + desc); 
					}
				}
				allDescriptors.put(desc.getId(), desc);