Bug 9159 Classpath wizard should not complain when adding missing source folder
Build 20020125 - Define a project A with source folder 'src1'. - Go to the .classpath file and edit it to insert one extra line: <classpathentry kind="src" path="src2"/> below the line referring to first source folder: <classpathentry kind="src" path="src1"/>. - Now, try to add this missing source folder 'src2', it isn't allowed by the wizard, one has to add a basic folder instead. Note: It is not such an uncommon scenario, the classpath modification could simply occur by catching up with a shared classpath having one more source folder on it, and which is locally missing.
org.eclipse.jdt.ui/ui/org/eclipse/jdt/internal/ui/wizards/buildpaths/BuildPathsBlock.java
private IJavaProject fCurrJProject;
		
	private IPath fOutputLocationPath;
	
	private IStatusChangeListener fContext;
	private Control fSWTWidget;	
	
	private boolean fShowSourceFolderPage;
	
	private SourceContainerWorkbookPage fSourceContainerPage;
	private ProjectsWorkbookPage fProjectsPage;
	private LibrariesWorkbookPage fLibrariesPage;
	
	private BuildPathBasePage fCurrPage;
		
	public BuildPathsBlock(IWorkspaceRoot root, IStatusChangeListener context, boolean showSourceFolders) {
		fWorkspaceRoot= root;
		fContext= context;
		
		fShowSourceFolderPage= showSourceFolders;
		
		
		fSourceContainerPage= null;
		fLibrariesPage= null;
		fProjectsPage= null;
		fCurrPage= null;
				
		BuildPathAdapter adapter= new BuildPathAdapter();			
	
		String[] buttonLabels= new String[] {