Added deNull().

git-svn-id: svn+ssh://src.earth.threerings.net/narya/trunk@5392 542714f4-19e9-0310-aa3c-eee0fc999fb1

src/as/com/threerings/util/StringUtil.as

@@ -53,6 +53,14 @@ public class StringUtil
         return (str == null) || (str.search("\\S") == -1);
     }
 
+    /**
+     * Return the specified String, or "" if it is null.
+     */
+    public static function deNull (str :String) :String
+    {
+        return (str == null) ? "" : str;
+    }
+
     /**
      * Does the specified string end with the specified substring.
      */