Bug: can not convert multiple fonts

[kisvegabor]

If you add multiple fonts to the online converter it fails with this error in the console:

Uncaught TypeError: Cannot read properties of undefined (reading 'symbols')
    at generate_opts_string (index.js:37907:16)
    at HTMLFormElement.handleSubmit (index.js:37987:22)

@neuschaefer, I think it's a regression due to the recent changes. Could you take a look at it?

[neuschaefer]

As far as I can see, it's fixed in #108. If that's not the case, could you provide the parameters that you entered when you got the error?

[kisvegabor]

I confirm that it's fixed by #108. Thank you!
The online converter is updated.