RFR: 8371092: NullPointerException in AltServiceUsageTest.afterClass() test

[Peyang]

On Sun, 2 Nov 2025 14:09:28 GMT, Peyang <duke at openjdk.org> wrote:

> - Add `safeClose(DatagramChannel)` to close udpNotResponding safely.
> - Null-check and exception handling unified with `safeStop()`.
> - Ensures test cleanup never fails due to uninitialized or problematic channel.

Thanks for your review.
I've run the test locally and confirmed it passes successfully.

-------------

PR Comment: https://git.openjdk.org/jdk/pull/28104#issuecomment-3485501240