Need a null check in GenBookBackend.getRawText

A null check is required in the following code in GenBookBackend.getRawText because find can return a null meaning that node, when used on the next line could be null:

DataPolice.setKey(key);
TreeNode node = find(key);
byte[] userData = node.getUserData();

// Some entries may be empty.
if (userData.length == 8) {

Here is a suggested fix but I don't know if you should return a null or an empty string in this scenario:

DataPolice.setKey(key);
TreeNode node = find(key);

// Is there an entry?
if (node == null)

{ return ""; }

byte[] userData = node.getUserData();

Here is a simple test:
Book book = getBook("Pilgrim");
Key key = book.getGlobalKeyList();
String rawText = book.getRawText(key);