ensure the nick timeout mechanism is cleaned up on client quit

irc/client.go

 	}
 
 	// clean up self
-	if client.idletimer != nil {
-		client.idletimer.Stop()
-	}
+	client.idletimer.Stop()
+	client.nickTimer.Stop()
 
 	client.server.accounts.Logout(client)
 

irc/idletimer.go

 
 // Stop stops counting idle time.
 func (it *IdleTimer) Stop() {
+	if it == nil {
+		return
+	}
+
 	it.Lock()
 	defer it.Unlock()
 	it.state = TimerDead
 	}
 }
 
+// Stop stops counting time and cleans up the timer
+func (nt *NickTimer) Stop() {
+	if nt == nil {
+		return
+	}
+
+	nt.Lock()
+	defer nt.Unlock()
+	if nt.timer != nil {
+		nt.timer.Stop()
+		nt.timer = nil
+	}
+}
+
 func (nt *NickTimer) sendWarning() {
 	baseNotice := "Nickname is reserved; you must change it or authenticate to NickServ within %v"
 	nt.client.Notice(fmt.Sprintf(nt.client.t(baseNotice), nt.timeout))