style(client): overlay frame show scrollbar

[btea]

Description

When the page displays an error message pop-up window, if the content is too long, it is more friendly to display a scrollbar.

Additional context

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What is the purpose of this pull request?

• Bug fix
• New Feature
• Documentation update
• Other

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• Read the Contributing Guidelines.
• Read the Pull Request Guidelines and follow the PR Title Convention.
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• Provide a description in this PR that addresses what the PR is solving, or reference the issue that it solves (e.g. fixes #123).
• Ideally, include relevant tests that fail without this PR but pass with it.

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[btea]

@bluwy Do you think this change is necessary?

[bluwy]

Personally, I don't really know 😄 But it doesn't hurt to add a scrollbar so I'm going to approve this as see what others think. It's only showing when there's long content so I think it's fine.

[sapphi-red]

I don't have a strong opinion but I think we can have this.