Unbreak running without a captive portal configuration file

dnscrypt-proxy/coldstart.go

@@ -22,7 +22,7 @@ type CaptivePortalHandler struct {
 	cancelChannels []chan struct{}
 }
 
-func (captivePortalHandler *CaptivePortalHandler) Stop() {
+func (captivePortalHandler *CaptivePortalHandler) Stop() {	
 	for _, cancelChannel := range captivePortalHandler.cancelChannels {
 		cancelChannel <- struct{}{}
 		_ = <-cancelChannel

dnscrypt-proxy/netprobe_others.go

@@ -14,7 +14,9 @@ func NetProbe(proxy *Proxy, address string, timeout int) error {
 		return nil
 	}
 	if captivePortalHandler, err := ColdStart(proxy); err == nil {
-		defer captivePortalHandler.Stop()
+		if captivePortalHandler != nil {
+			defer captivePortalHandler.Stop()
+		}
 	} else {
 		dlog.Critical(err)
 	}

dnscrypt-proxy/netprobe_windows.go

@@ -12,7 +12,9 @@ func NetProbe(proxy *Proxy, address string, timeout int) error {
 		return nil
 	}
 	if captivePortalHandler, err := ColdStart(proxy); err == nil {
-		defer captivePortalHandler.Stop()
+		if captivePortalHandler != nil {
+			defer captivePortalHandler.Stop()
+		}
 	} else {
 		dlog.Critical(err)
 	}