fix(safari): fixes an exception that is caused by adding a null stream to pc

Remove unused code, we always use replaceTrack in unified plan

modules/RTC/TPCUtils.js

@@ -257,10 +257,14 @@ export class TPCUtils {
         // If the client starts with audio/video muted setting, the transceiver direction
         // will be set to 'recvonly'. Use addStream here so that a MSID is generated for the stream.
         if (transceiver.direction === 'recvonly') {
-            this.pc.peerconnection.addStream(localTrack.getOriginalStream());
-            this.setEncodings(localTrack);
-            this.pc.localTracks.set(localTrack.rtcId, localTrack);
-            transceiver.direction = 'sendrecv';
+            const stream = localTrack.getOriginalStream();
+
+            if (stream) {
+                this.pc.peerconnection.addStream(localTrack.getOriginalStream());
+                this.setEncodings(localTrack);
+                this.pc.localTracks.set(localTrack.rtcId, localTrack);
+                transceiver.direction = 'sendrecv';
+            }
 
             return Promise.resolve(false);
         }

modules/RTC/TraceablePeerConnection.js

@@ -1606,9 +1606,6 @@ TraceablePeerConnection.prototype.isMediaStreamInPc = function(mediaStream) {
  *       The same applies to addTrack.
  */
 TraceablePeerConnection.prototype.removeTrack = function(localTrack) {
-    if (browser.usesUnifiedPlan()) {
-        return this.tpcUtils.removeTrack(localTrack);
-    }
     const webRtcStream = localTrack.getOriginalStream();
 
     this.trace(