cask/cask: rescue with no method

[bevanjkay]

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I used claude-code to help debug the issue.

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As discovered in https://github.com/Homebrew/homebrew-cask/actions/runs/21855449950/job/63071483158?pr=248614 there are instances where the version can be invalid on a specific architecture, in this case the generation fails for the Linux map because the version is only referenced in on_{os} blocks, and the url is at the top-level. This should catch the error and skip for the architectures that are invalid.

[MikeMcQuaid]

Looks good thanks!

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