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?

I don't have a solution that works with Fluid, but Aluxian/WhatsApp-Desktop on GitHub provides an open-source wrapper for the WhatsApp web app which works well and provides similar functionality to what Fluid would.

Stumbled upon the same, but I found a very good wrapper for whatsapp that feels very well integrated with OSX look&feel: ChitChat. It being OSS is a great plus for me.