Cannot start PROXX in private mode in Firefox

[NotWoods]

Debug info

    Version: 1.0.9
    Motion: true
    Supports WebGL: true
    Feature Phone: no
    Standalone Mode: no
    Screen Width: 1680px
    Screen Height: 913px
    DPR: 2
    Device Memory:
    Concurrency: 6
    UA: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.14; rv:73.0) Gecko/20100101 Firefox/73.0

Describe the bug
When you open PROXX in Private Mode in Firefox, it is impossible to start the game. All form fields have no values set, preventing the start button from working.

Its likely that PROXX fails when IndexedDB isn't present, as is the case in private mode.

Originally reported here: mozilla-mobile/fenix#7293

To Reproduce
Steps to reproduce the behaviour:

1. Open a Private tab in Firefox
2. Go to proxx.app
3. See that all fields are empty
4. Click start and see that it doesn't react due to failed form validation

Expected behavior
Start the game :)