server: cleanup user in defer

If a user goroutine panics, this correctly removes it from the
global map instead of leaving a dangling entry behind.

server.go

@@ -286,9 +286,6 @@ func (s *Server) addUserLocked(user *User) *user {
 			if err := recover(); err != nil {
 				s.Logger.Printf("panic serving user %q: %v\n%v", user.Username, err, debug.Stack())
 			}
-		}()
-
-		u.run()
 
 			s.lock.Lock()
 			delete(s.users, u.Username)
@@ -297,6 +294,9 @@ func (s *Server) addUserLocked(user *User) *user {
 			s.stopWG.Done()
 		}()
 
+		u.run()
+	}()
+
 	return u
 }