[Bug]: New workflow won't save due to regression with profileid field

[tw4l]

Browsertrix Version

v1.11.0-beta.1-f7a675ea

What did you expect to happen? What happened instead?

I expect that a new workflow with the default browser profile will save and start a crawl.

Instead I get the following error: profileid value is not a valid uuid

Reproduction instructions

1. Try to create a workflow with the default profile
2. Watch it fail

Screenshots / Video

No response

Environment

No response

Additional details

It looks like this is a regression from #1935 - profileid in CrawlConfigIn was previously type Union[UUID, EmptyStr, None] and would set an empty string to None in the ops method before creating the workflow in the database. Now that it's just Optional[UUID], the frontend passing an empty string instead causes the workflow not to save.

The changes in #1935 make sense for the backend, we should make sure the frontend passes None rather than an empty string if no browser profile is set.