[#1628] Avoid exception caused by calling release multiple times

[wForget]

What changes were proposed in this pull request?

Set internal buffer to null after release.

Why are the changes needed?

address https://github.com/apache/incubator-uniffle/issues/1628#issuecomment-2182902051

Fix: #1628

Does this PR introduce any user-facing change?

No.

How was this patch tested?

added unit tests