remove unnecessary indirection in config

irc/config.go

 	Debug struct {
 		RecoverFromErrors *bool `yaml:"recover-from-errors"`
 		recoverFromErrors bool
-		PprofListener     *string `yaml:"pprof-listener"`
+		PprofListener     string `yaml:"pprof-listener"`
 	}
 
 	Limits Limits

irc/server.go

 }
 
 func (server *Server) setupPprofListener(config *Config) {
-	pprofListener := ""
-	if config.Debug.PprofListener != nil {
-		pprofListener = *config.Debug.PprofListener
-	}
+	pprofListener := config.Debug.PprofListener
 	if server.pprofServer != nil {
 		if pprofListener == "" || (pprofListener != server.pprofServer.Addr) {
 			server.logger.Info("server", "Stopping pprof listener", server.pprofServer.Addr)