RFR: Fix NullPointerException on a parallel run [v5]

[Dmitry Bessonov]

On Thu, 1 Sep 2022 12:12:12 GMT, Jan Kratochvil <duke at openjdk.org> wrote:

> It won't generate NPE but it will produce `String "null/filename"`. Which will produce NPE later in the code like the original problem this patch tries to fix. But then we do not know what return value `null` from `getRootRelativePath()` should mean. So we do not know what to do with such return value anyway. But I prefer it this way, thanks for the approval.

you are right, as a follow up I'd update the code to


                    processFile(path == null || path.isEmpty() // Zero length string if the node is a root

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PR: https://git.openjdk.org/jtharness/pull/35