fix: correct ICS20 middleware handlers

[robert-zaremba]

Description

Updates related to the ICS20 middleware research and audit.

• fix related to acknowledgment error deserialization.

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Author Checklist

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I have...

• included the correct type prefix in the PR title
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• added a changelog entry to CHANGELOG.md
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• reviewed state machine logic
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• reviewed tests and test coverage
• manually tested (if applicable)

[gsk967]

small nit , everything LGTM