WhatsApp Web in Fluid throws JavaScript exception

When I'm starting the WhatsApp web client in a Fluid app, this JavaScript exception is thrown: [Error] TypeError: undefined is not an object (evaluating 'e.getDatabaseNames') U (app_59f797fae4fc761b3ee8.js, line 63) c (app_59f797fae4fc761b3ee8.js, line 62) n (app_59f797fae4fc761b3ee8.js, line 6) (anonymous function) (app_59f797fae4fc761b3ee8.js, line 6) t (app_59f797fae4fc761b3ee8.js, line 5) (anonymous function) (app_59f797fae4fc761b3ee8.js, line 5) t (app_59f797fae4fc761b3ee8.js, line 5) (anonymous function) (app_59f797fae4fc761b3ee8.js, line 5) webpackJsonp (app_59f797fae4fc761b3ee8.js, line 5) global code (crypto_8cbbef38a0cf6ff138dc.js, line 2) This leads an infinite loading screen. When I launch WhatsApp Web in Safari e is a IDBFactory, but it looks like the IndexedDB API isn't available in a Fluid app (there e is null). You have to set either Firefox, Chrome or Safari as user agent to get to the loading screen. I tried playing around with the settings, but nothing seems to help. I wrote a mail to the FluidApp support, but no answer so far. Does anyone have advice?