fix: this._implicitHeader is not a function

[Niputi]

Description

possibly fix: #2754

Additional context

references: Alorel/shrink-ray#55 nginx/unit@7b839bf

I have been unable to reproduce the issue on my windows 11 computer with firefox / edge / chrome so I can't verify if it will be fixed

would be great if someone would be able to maintain a new version compression as it looks heavily outdated/unmaintained

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What is the purpose of this pull request?

• Bug fix
• New Feature
• Documentation update
• Other

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