When someone leaves a team, the team will became unfunctional.
The team still exists, appears within "/team list" and entities can join and be targeted (team=<team>).
However, the team doesn't shows within "/team join" or "/team modify" auto-complete and teams properties (color / collision rule) doesn't work.
How to reproduce:
- Create a dummy team
/team add dummy
- Modify one of the properties of the team
/team modify dummy color aqua
- Make you and an entity join the team
/team join dummy @s
/team join dummy @e[type=!player,limit=1]
- Remove the entity from the team
/team leave @e[type=!player,team=dummy]
- The team is now unusable
Console output when joining/leaving the team: