8350542: Optional.orElseThrow(Supplier) does not specify behavior when supplier returns null

Reviewed-by: liach, clanger

Author: gustavosimon

src/java.base/share/classes/java/util/Optional.java

@@ -394,7 +394,7 @@ public T orElseThrow() {
      * @return the value, if present
      * @throws X if no value is present
      * @throws NullPointerException if no value is present and the exception
-     *          supplying function is {@code null}
+     *         supplying function is {@code null} or produces a {@code null} result
      */
     public <X extends Throwable> T orElseThrow(Supplier<? extends X> exceptionSupplier) throws X {
         if (value != null) {