R1:ce6fc5be9092

Fix a looping workflow when trying to submit a partially-effectless transaction group

Summary:
Ref T13289. If you do this:

- Subscribe to a task (so we don't generate a subscribe side-effect later).
- Prepare a transaction group: sign with MFA, change projects (don't make any changes), add a comment.
- Submit the transaction group.

...you'll get prompted "Some actions don't have any effect (the non-change to projects), apply remaining effects?".

If you confirm, you get MFA'd, but the MFA flow…