RFR: 8300731: Avoid unnecessary array fill after creation in PaletteBuilder

[Phil Race]

On Thu, 19 Jan 2023 19:32:05 GMT, Andrey Turbanov <aturbanov at openjdk.org> wrote:

> No need to fill elements of array with `null`: it was just created. Java guarantees that all elements of array are `null`s anyway.

Marked as reviewed by prr (Reviewer).

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PR: https://git.openjdk.org/jdk/pull/12101