RFR [9] 8053938: Collections.checkedList(empty list).replaceAll((UnaryOperator)null) doesn't throw NPE after JDK-8047795

[Chris Hegarty]

A trivial one-liner for a missing null check for the given operator 
after the changes for 8047795, which now always passes a non-null 
operator to the underlying list.replaceAll.

The original test has been updated in it's existing style to cover this.

http://cr.openjdk.java.net/~chegar/8053938/webrev.00/webrev/

-Chris.