Fix temporary call messages being handled without call

In cases where a rogue client, or just a simple bug, sends a temporary
call message, like CallNegotiate the messages should just be discarded
if there's no actual p2p connection created.

src/webrtc/call.ts

@@ -1286,7 +1286,7 @@ export class MatrixCall extends EventEmitter {
         // https://developer.mozilla.org/en-US/docs/Web/API/WebRTC_API/Perfect_negotiation
         const offerCollision = (
             (description.type === 'offer') &&
-            (this.makingOffer || this.peerConn.signalingState != 'stable')
+            (this.makingOffer || this.peerConn.signalingState !== 'stable')
         );
 
         this.ignoreOffer = !polite && offerCollision;
@@ -1935,6 +1935,10 @@ export class MatrixCall extends EventEmitter {
             }
         }
     }
+
+    get hasPeerConnection() {
+        return Boolean(this.peerConn);
+    }
 }
 
 async function getScreensharingStream(

src/webrtc/callEventHandler.ts

@@ -220,6 +220,7 @@ export class CallEventHandler {
             } else {
                 this.client.emit("Call.incoming", call);
             }
+            return;
         } else if (type === EventType.CallCandidates) {
             if (weSentTheEvent) return;
 
@@ -232,6 +233,7 @@ export class CallEventHandler {
             } else {
                 call.onRemoteIceCandidatesReceived(event);
             }
+            return;
         } else if ([EventType.CallHangup, EventType.CallReject].includes(type)) {
             // Note that we also observe our own hangups here so we can see
             // if we've already rejected a call that would otherwise be valid
@@ -255,10 +257,14 @@ export class CallEventHandler {
                     this.calls.delete(content.call_id);
                 }
             }
+            return;
         }
 
-        // The following events need a call
+        // The following events need a call and a peer connection
-        if (!call) return;
+        if (!call && !call.hasPeerConnection) {
+            logger.warn('Discarding an event', type);
+            return;
+        }
         // Ignore remote echo
         if (event.getContent().party_id === call.ourPartyId) return;