RFR: 7473: Unable to view constants in constant pool page. [v2]

[Marcus Hirt]

On Mon, 10 Jan 2022 16:26:02 GMT, Alex Macdonald <aptmac at openjdk.org> wrote:

>> This PR addresses JMC-7473 [[0]](https://bugs.openjdk.java.net/browse/JMC-7473), in which the Constant Pools page throws an exception and does not display. The issue here is in ParserStats, and happens if the stacktrace object doesn't have any frames - but there is a retrieval for the first frame. 
>> 
>> Before:
>> ![2022-01-10-105031_790x151_scrot](https://user-images.githubusercontent.com/10425301/148796099-b32c4802-7b12-4489-ab09-0aa65a73cea9.png)
>> 
>> After:
>> ![2022-01-10-105044_668x458_scrot](https://user-images.githubusercontent.com/10425301/148796118-d066f332-d0a3-4982-9502-b26efd2ef01b.png)
>
> Alex Macdonald has updated the pull request incrementally with one additional commit since the last revision:
> 
>   spotless

Marked as reviewed by hirt (Lead).

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PR: https://git.openjdk.java.net/jmc/pull/348