Fix closeable panic

Fix closeable panic when conn == nil

README.md

@@ -48,6 +48,7 @@ Check out the **[contributing wiki](https://github.com/pion/webrtc/wiki/Contribu
 * [Jason Maldonis](https://github.com/jjmaldonis)
 * [Nevio Vesic](https://github.com/0x19)
 * [David Hamilton](https://github.com/dihamilton)
+* [adwpc](https://github.com/adwpc)
 
 ### License
 MIT License - see [LICENSE](LICENSE) for full text

gather.go

@@ -22,6 +22,11 @@ type closeable interface {
 
 // Close a net.Conn and log if we have a failure
 func closeConnAndLog(c closeable, log logging.LeveledLogger, msg string) {
+	if c == nil {
+		log.Warnf("Conn is not allocated")
+		return
+	}
+
 	log.Warnf(msg)
 	if err := c.Close(); err != nil {
 		log.Warnf("Failed to close conn: %v", err)