Fix: When previewing SVG, report error "Failed to execute 'btoa' on '…

…Window': The string to be encoded contains characters outside of the Latin1 range."

When previewing SVG, report error:

`viewer-main.mjs?v=79b66689-10:588 Error evaluating async computed property: Error: Failed to execute 'btoa' on 'Window': The string to be encoded contains characters outside of the Latin1 range.`

ref: https://stackoverflow.com/questions/23223718/failed-to-execute-btoa-on-window-the-string-to-be-encoded-contains-characte

Signed-off-by: XinRoom <32238570+XinRoom@users.noreply.github.com>

Signed-off-by: nextcloud-command <nextcloud-command@users.noreply.github.com>