pdf source doesn't show up while pages and filename are shown correctly

[jubusch]

Hi first of all thank you for this great element.
Unfortunately I can't get it to work out of the box.
Everything is working correctly, except the pdf doesn't show up. Instead a white square minimizes to a small dot on the left.
I only get this warning:
pdf.worker.js:23916 The provided value 'moz-chunked-arraybuffer' is not a valid enum value of type XMLHttpRequestResponseType.
It would be great if someone could help me out, thanks in advance.