Avoid crashes when closing peer connection client.

// FREEBIE

Signal/src/call/PeerConnectionClient.swift

@@ -453,10 +453,6 @@ class PeerConnectionClient: NSObject, RTCPeerConnectionDelegate, RTCDataChannelD
         localVideoTrack?.isEnabled = false
         remoteVideoTrack?.isEnabled = false
 
-        peerConnection.delegate = nil
-        peerConnection.close()
-        peerConnection = nil
-
         dataChannel = nil
         audioSender = nil
         audioTrack = nil
@@ -464,6 +460,10 @@ class PeerConnectionClient: NSObject, RTCPeerConnectionDelegate, RTCDataChannelD
         localVideoTrack = nil
         remoteVideoTrack = nil
 
+        peerConnection.delegate = nil
+        peerConnection.close()
+        peerConnection = nil
+
         delegate = nil
     }