non-latin1 characters used with "sandbox" throws and renders iframe in weird spot

[hojberg]

Description

When using the "sandbox" setting along side a diagram with non-latin1 characters in them the following occurs:

1. An error is thrown:

Uncaught DOMException: Failed to execute 'btoa' on 'Window': The string to be encoded contains characters outside of the Latin1 range.

2. Instead of not rendering anything, Mermaid, unexpectedly, renders the iframe with the svg (and rendered correctly it seems), at the bottom of the page just before the </body> tag.

Here's the example diagram, notice the ∘ (compose) character:

flowchart TB
  A["f ∘ g"]

Steps to reproduce

Here's a full example: https://jsfiddle.net/s3817cjq/8/

Screenshots

No response

Code Sample

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Setup

Desktop

• OS and Version: Mac
• Browser and Version: Chrome

Additional Context

No response