Made sanitize() cope with null.

git-svn-id: https://samskivert.googlecode.com/svn/trunk@1808 6335cc39-0255-0410-8fd6-9bcaacd3b74c

src/java/com/samskivert/util/StringUtil.java

@@ -123,6 +123,9 @@ public class StringUtil
      */
     public static String sanitize (String source, CharacterValidator validator)
     {
+        if (source == null) {
+            return null;
+        }
         int nn = source.length();
         StringBuffer buf = new StringBuffer(nn);
         for (int ii=0; ii < nn; ii++) {