Bug 120544 [build path] Editing external source folder does not persist
org.eclipse.jdt.ui/ui/org/eclipse/jdt/internal/ui/wizards/buildpaths/CPListElement.java
IClasspathContainer container= JavaCore.getClasspathContainer(fPath, fProject);
					if (container != null) {
						IClasspathEntry[] entries= container.getClasspathEntries();
						for (int i= 0; i < entries.length; i++) {
							IClasspathEntry entry= entries[i];
							if (entry != null) {
								CPListElement curr= createFromExisting(this, entry, fProject);
								fChildren.add(curr);
							} else {
								JavaPlugin.logErrorMessage("Null entry in container '" + fPath + "'");  
							}
						}						
					}
				} catch (JavaModelException e) {
				}			
				break;
			default:
		}
		
	}
	
	public IClasspathEntry getClasspathEntry() {
		if (fCachedEntry == null) {
			fCachedEntry= newClasspathEntry();
		}
		return fCachedEntry;
	}
	
	
	private IClasspathAttribute[] getClasspathAttributes() {