Element iOS sends you to Element Web after email validation

[clokep]

If email validation is enabled on registration you can end up in an odd state:

1. Do registration via iOS, this gives a throbber while it checks that you've verified e-mail.
2. Verify the e-mail by clicking on the link and letting it open in a browser.
3. Get redirected to Element Web, which now races with Element iOS to complete registration.
4. I saw one of two behaviors at this point:
   1. Both session login successfully, but one prompts you to validate the other.
   2. One session logs in successfully, the other sits there on a loading throbber forever.

I was seeing this very clearly when opening the validation link on a desktop. Does Element iOS purposefully set the next_link parameter to Element Web when generating an e-mail validation? It seems like it could lead to undesired behavior.

I found this while working on matrix-org/synapse#8009, although it is not directly related to that.