Example doesn't work in Firefox

[zavod]

Hello! I'm trying to run IDBWrapper Quick Test in Firefox 60 and got issue:
"InvalidStateError: A mutation operation was attempted on a database that did not allow mutations."
The screen is here http://prntscr.com/jil3mf
How can I fix it?

[jensarps]

Thanks for reporting this!

That's a weird error you ran into there...

Did you run any of the IDBWrapper examples before? Can you check in the "storage" panel of the developer tools if there is an existing IndexedDB store? Thanks!