[FIX] mail: remove the dataChannel entry when removing a peer.

Before this commit, the entry in `mailRtc._dataChannels` was not removed
when removing a peer, which meant that `mailRtc._dataChannels` could
contain old closed dataChannels. Moreover, the call to `close()` on the
dataChannel was not guarded, which could lead to tracebacks.

For example, if a peer was removed before creating its dataChannel (like
in crashes or successive connection recovery attempts), `close()` was
called on `undefined`.

this commit fixes this issue.

closes odoo/odoo#77880

X-original-commit: da3fce19157a07fc1abbb6d188746d4a00d3a344
Signed-off-by: Sébastien Theys (seb) <seb@odoo.com>

addons/mail/static/src/models/rtc/rtc.js

@@ -772,9 +772,12 @@ function factory(dependencies) {
             if (rtcSession) {
                 rtcSession.reset();
             }
-            const peerConnection = this._peerConnections[token];
             const dataChannel = this._dataChannels[token];
-            dataChannel.close();
+            if (dataChannel) {
+                dataChannel.close();
+            }
+            delete this._dataChannels[token];
+            const peerConnection = this._peerConnections[token];
             if (peerConnection) {
                 this._removeRemoteTracks(peerConnection);
                 peerConnection.close();