[FIX] discuss: prevent peer-to-peer update without a RTCPeerConnection

Before this commit, it was possible that an attempt to update
peer connections made right at the moment the connection was swapped
from peer-to-peer to server mode. Which would cause a traceback.

This commit fixes this issue by checking if there is a
`RTCPeerConnection` before trying to update it.

closes odoo/odoo#148505

Signed-off-by: Sébastien Theys (seb) <seb@odoo.com>

addons/mail/static/src/discuss/call/common/rtc_service.js

@@ -1494,6 +1494,9 @@ export class Rtc {
      * negotiationneeded -> offer -> answer -> ...
      */
     async updateRemote(session, trackKind) {
+        if (!session.peerConnection) {
+            return;
+        }
         this.log(session, `updating ${trackKind} transceiver`);
         let track;
         switch (trackKind) {