Killing any enemy prevents other enemies to relay chat messages

**Methodology:**
1. Add 3 random chat participants as enemies in AbstractRoom
2. Send 1 message from each one
3. Kill any enemy
4. Send message from remaining two enemies

**Actual result:**
At step 2 all 3 enemies will relay chat message.
At step 4 none of enemies will relay chat message.

**Expected Result:**
At step 4 two remaining enemies continue relaying messages.