device/webcam: don't close closed chan

device/webcam/webcam.go

@@ -197,6 +197,10 @@ func (w *Webcam) Start() error {
 
 // Stop will kill the ffmpeg process and close the output pipe.
 func (w *Webcam) Stop() error {
+	if !w.isRunning {
+		return nil
+	}
+	w.isRunning = false
 	close(w.done)
 	if w.cmd == nil || w.cmd.Process == nil {
 		return errors.New("ffmpeg process was never started")
@@ -205,12 +209,7 @@ func (w *Webcam) Stop() error {
 	if err != nil {
 		return fmt.Errorf("could not kill ffmpeg process: %w", err)
 	}
-	err = w.out.Close()
-	if err == nil {
-		w.isRunning = false
-		return nil
-	}
-	return err
+	return w.out.Close()
 }
 
 // Read implements io.Reader. If the pipe is nil a read error is returned.