Error thrown: Firestore has already been started and persistence can no longer be enabled

I see you are throwing an error in certain situations when trying to setup firebase offline persistence:

https://github.com/firebase/firebase-js-sdk/blob/f5426a51275bb611a5d9a6df3200d0fe5095afa2/packages/firestore/src/api/database.ts#L561-L565

This is completely unexpected, not documented and I think it is a bad idea. The documentation says that, in case of error you will get a rejected promise, which is what I am coding for and what I a m guarding against, however, to my surprise a plain sync error is just thrown and therefore I am not notified in any way.
Please, consider fixing this and adding it to the list of possible rejection values in the returned promise