Javadoc tweak

git-svn-id: https://svn.apache.org/repos/asf/commons/proper/lang/trunk@966173 13f79535-47bb-0310-9956-ffa450edef68

src/main/java/org/apache/commons/lang3/BooleanUtils.java

@@ -692,7 +692,7 @@ public static Boolean toBooleanObject(String str, String trueString, String fals
      * </pre>
      *
      * @param str  the String to check
-     * @return the boolean value of the string, <code>false</code> if no match
+     * @return the boolean value of the string, <code>false</code> if no match or the String is null
      */
     public static boolean toBoolean(String str) {
         return toBooleanObject(str) == Boolean.TRUE;