/team join and /team leave are always successful

The bug

/team join and /team leave are always successful, even if the team has already a member with the given name respectively the team has no member with that name.

How to reproduce

1. Create a team and join it

   /team add test
   /team join test @s
   

2. Try to join it again

   /team join test @s
   

   → It says that you joined the team despite already being a member