do not downcast activities to the wrong type just to get their name

do not downcast activities to the wrong type just to get their name

- I use a protected method to keep my data private. Doing otherwise
  would trigger sonar to complain.
- The code is not particularly clear this way, but I fail to see how
  to do otherwise: I don't want the getter to become a virtual method.
- This was reported by UndefSan now that we have a test that deadlocks.