RFR: Fix NullPointerException on a parallel run [v3]

[Jan Kratochvil]

On Thu, 1 Sep 2022 10:23:16 GMT, Dmitry Bessonov <dbessono at openjdk.org> wrote:

>> `getRootRelativePath()` can never return `null`: https://github.com/openjdk/jtharness/blob/b9f4a2c03135208608b7e1a6586be6fe57a062d6/src/com/sun/javatest/TestResultTable.java#L338
>> The `NullPointerException` happens later in the code because the wrongly computed filename does not exist. (That could be an unrelated bug whether it should not be handled better, for example in the case someone deletes such file underneath.)
>
> @jankratochvil thanks for the update. I guess even if some method now doesn't return null, we'd be better prepared if it starts in future due to some refactoring.
> 
> Can see that the recent change failed jcheck
> 
> Check failure on line 808 in src/com/sun/javatest/TRT_TreeNode.java
> openjdk / jcheck
> 
> Whitespace error
> 
> Column 50: trailing whitespace
> 
> 
> 
> Once jcheck is OK, I guess we might be good to go to resolve the issues you are facing with a parallel run

@dbessono I am not sure - is this patch OK or should I check whether `getRootRelativePath()` has returned `null`?
Otherwise I have fixed the whitespace, sorry for not noticing the `jcheck` error, it sends no mails.

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