Bug 11437 jar packager: no error message but buttons disabled
20020314 on the 'jar manifest' wizard page, if you select to use existing manifest file there's no error message but next and finish are disabled user should be informed what to do to make the wizard happy
org.eclipse.jdt.ui/ui/org/eclipse/jdt/internal/ui/jarpackager/JarManifestWizardPage.java
* 
	 * @param packageFragments the package fragments
	 * @return a new selection dialog
	 */
	protected SelectionDialog createPackageDialog(Set packageFragments) {
		List packages= new ArrayList(packageFragments.size());
		for (Iterator iter= packageFragments.iterator(); iter.hasNext();) {
			IPackageFragment fragment= (IPackageFragment)iter.next();
			boolean containsJavaElements= false;
			int kind;
			try {
				kind= fragment.getKind();
				containsJavaElements= fragment.getChildren().length > 0;
			} catch (JavaModelException ex) {
				ExceptionHandler.handle(ex, getContainer().getShell(), JarPackagerMessages.getString("JarManifestWizardPage.error.jarPackageWizardError.title"), JarPackagerMessages.getFormattedString("JarManifestWizardPage.error.jarPackageWizardError.message", fragment.getElementName())); 
				continue;
			}
			if (kind != IPackageFragmentRoot.K_BINARY && containsJavaElements)
				packages.add(fragment);
		}
		JavaElementContentProvider cp= new JavaElementContentProvider() {
			public boolean hasChildren(Object element) {
				
				return !(element instanceof IPackageFragment) && super.hasChildren(element);
			}
		};
		ElementTreeSelectionDialog dialog= new ElementTreeSelectionDialog(getContainer().getShell(), new JavaElementLabelProvider(JavaElementLabelProvider.SHOW_DEFAULT), cp);
		dialog.setDoubleClickSelects(false);
		dialog.setInput(JavaCore.create(JavaPlugin.getDefault().getWorkspace().getRoot()));
		dialog.addFilter(new EmptyInnerPackageFilter());