Bug 53201 NPE when re-running newly generated javadoc.xml
org.eclipse.jdt.ui/ui/org/eclipse/jdt/internal/ui/javadocexport/JavadocOptionsManager.java
public void setJDK14Mode(boolean jdk14Mode) {
		fJDK14Mode= jdk14Mode;
	}	
	private IJavaElement[] getInitialElementsFromSelection(List candidates) {
		ArrayList res= new ArrayList();
		for (int i= 0; i < candidates.size(); i++) {
			try {
				IJavaElement elem= getSelectableJavaElement(candidates.get(i));
				if (elem != null) {
					res.add(elem);
				}
			} catch (JavaModelException ignore) {
				
			}
		}
		return (IJavaElement[]) res.toArray(new IJavaElement[res.size()]);
	}
	private IJavaElement getSelectableJavaElement(Object obj) throws JavaModelException {
		IJavaElement je= null;
		if (obj instanceof IAdaptable) {
			je= (IJavaElement) ((IAdaptable) obj).getAdapter(IJavaElement.class);
		}
		if (je != null) {
			switch (je.getElementType()) {
				case IJavaElement.JAVA_MODEL :
				case IJavaElement.JAVA_PROJECT :
				case IJavaElement.CLASS_FILE :
					break;
				case IJavaElement.PACKAGE_FRAGMENT_ROOT :
					if (containsCompilationUnits((IPackageFragmentRoot) je)) {