RFR: Fix a crash with IntelliJ 2020.2 [v2]

[Maurizio Cimadamore]

On Mon, 22 Mar 2021 11:35:08 GMT, Maurizio Cimadamore <mcimadamore at openjdk.org> wrote:

>> Liam Miller-Cushon has refreshed the contents of this pull request, and previous commits have been removed. The incremental views will show differences compared to the previous content of the PR.
>
> Looks good - typically we add notes of what changed in the plugin file (resources/plugin.xml) and we bump the version number.
> Also, I suspect this fix has some implication when it comes to backward compatibility - currently we state:
> `    <idea-version since-build="162.0"/>`
> Should we rectify that?

Btw - this also needs a bug to be opened under the CodeTools project (tool = jtreg).

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PR: https://git.openjdk.java.net/jtreg/pull/5