Don't hide mismatches in the PeerConnection state automaton.

The previous behaviour led to silent failures, which was confusing.

rtpconn/webclient.go

@@ -569,9 +569,6 @@ func gotAnswer(c *webClient, id string, sdp string) error {
 		return ErrUnknownId
 	}
 
-	if down.pc.SignalingState() == webrtc.SignalingStateStable {
-		log.Printf("Got answer in stable state -- this shouldn't happen")
-	} else {
 	err := down.pc.SetRemoteDescription(webrtc.SessionDescription{
 		Type: webrtc.SDPTypeAnswer,
 		SDP:  sdp,
@@ -579,7 +576,6 @@ func gotAnswer(c *webClient, id string, sdp string) error {
 	if err != nil {
 		return err
 	}
-	}
 
 	for _, t := range down.tracks {
 		local := t.track.Codec()
@@ -590,7 +586,7 @@ func gotAnswer(c *webClient, id string, sdp string) error {
 		}
 	}
 
-	err := down.flushICECandidates()
+	err = down.flushICECandidates()
 	if err != nil {
 		log.Printf("ICE: %v", err)
 	}