[Bug] App hangs when Coach selects a team with no sessions

_A feature will address this:_ Coach can create the first session for a team that has no sessions or enrollments

At the earliest stages of a season or newly forming program site, a team and team season may exist but not have any players enrolled yet and no sessions scheduled.
The app should permit the coach to build the season ad-hoc if necessary, by adding sessions as needed.

**UX**

1. The Coach selects the Team Season
2. A message appears: There are no sessions in the selected season ___________ for this team. Do you want to add one? [Add Session][Cancel]
3. Coach selects [Add Session] If they select [Cancel], navigate to the previous list view
4. The Session Add view is presented.

**Consideration**:
- The Coach should be able to use the Enroll feature to add students quickly