URL: https://wa.me/97237401333

Browser / Version: Firefox 66.0
Operating System: Windows 10
Tested Another Browser: Yes

Problem type: Site is not usable
Description: Whatsapp API does not work on Firefox
Steps to Reproduce:
When opening the above link in Firefox (with all addons disabled), the page gets redirected to:

whatsapp://send?phone=97237401333&text=&source=&data=

Then the following error page appears (screenshot attached

Submitted in the name of @toldry

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