NewCookieHeaderDelegate throws if NewCookie value is null

Almost everywhere (constructors, equals(), hashCode(), CookieHeaderDelegate) it's OK to have a null value for a NewCookie (or Cookie), but NewCookieHeaderDelegate throws a NullPointerException in this case.

This is due to eventually calling MediaTypeHeaderDelegate.quoted() with a null value, where that methods calls getCharArray() on its argument without null-check.