veyron/lib/websocket: Fix bug in conn_nacl.

Unfortunately unrelated to all the other bugs.

Change-Id: Icff27d73829bf395e1edbf3e172a4c58e5bfffe2
diff --git a/lib/websocket/conn_nacl.go b/lib/websocket/conn_nacl.go
index 22d368d..e20ced8 100644
--- a/lib/websocket/conn_nacl.go
+++ b/lib/websocket/conn_nacl.go
@@ -50,7 +50,7 @@
 	if len(c.currBuffer) == 0 {
 		c.currBuffer, err = c.ws.ReceiveMessage()
 		if err != nil {
-			return 0, nil
+			return 0, err
 		}
 	}