x/image/font/sfnt: fix io.EOF in ParseReaderAt on fonts with useMarkFilteringSet

[matstech]

Fixes an io.EOF returned by ParseReaderAt when parsing fonts with a
GPOS Extension lookup (type 9) and the useMarkFilteringSet flag set.

Fixes golang/go#79489

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[dpiauxdda]

Hey guys, is 1:30 in the morning can I get some rest please? I went to bed hotOn May 20, 2026, at 01:12, GopherBot ***@***.***> wrote:gopherbot left a comment (golang/image#32) Message from Gopher Robot: Patch Set 1: Congratulations on opening your first change. Thank you for your contribution! Next steps: A maintainer will review your change and provide feedback. See https://go.dev/doc/contribute#review for more info and tips to get your patch through code review. Most changes in the Go project go through a few rounds of revision. This can be surprising to people new to the project. The careful, iterative review process is our way of helping mentor contributors and ensuring that their contributions have a lasting impact. Please don’t reply on this GitHub thread. Visit golang.org/cl/779862. After addressing review feedback, remember to publish your drafts! —Reply to this email directly, view it on GitHub, or unsubscribe.You are receiving this because you are subscribed to this thread.Message ID: ***@***.***>