Don't use event.sender in CallMembership (#3793)

* Don't use event.sender in CallMembership

I fell into another js-sdk trap: this is "only guaranteed to be set
for events that appear in a timeline" and not state events. It does
not say why. We only ever used it to get the sender user ID anyway,
so just use getSender().

* Fix test

spec/unit/matrixrtc/CallMembership.spec.ts

@@ -29,9 +29,7 @@ const membershipTemplate: CallMembershipData = {
 function makeMockEvent(originTs = 0): MatrixEvent {
     return {
         getTs: jest.fn().mockReturnValue(originTs),
-        sender: {
-            userId: "@alice:example.org",
-        },
+        getSender: jest.fn().mockReturnValue("@alice:example.org"),
     } as unknown as MatrixEvent;
 }
 

src/matrixrtc/CallMembership.ts

@@ -14,7 +14,7 @@ See the License for the specific language governing permissions and
 limitations under the License.
 */
 
-import { MatrixEvent, RoomMember } from "../matrix";
+import { MatrixEvent } from "../matrix";
 import { deepCompare } from "../utils";
 import { Focus } from "./focus";
 
@@ -42,11 +42,11 @@ export class CallMembership {
         if (typeof data.device_id !== "string") throw new Error("Malformed membership event: device_id must be string");
         if (typeof data.call_id !== "string") throw new Error("Malformed membership event: call_id must be string");
         if (typeof data.scope !== "string") throw new Error("Malformed membership event: scope must be string");
-        if (!parentEvent.sender) throw new Error("Invalid parent event: sender is null");
+        if (!parentEvent.getSender()) throw new Error("Invalid parent event: sender is null");
     }
 
-    public get member(): RoomMember {
-        return this.parentEvent.sender!;
+    public get sender(): string | undefined {
+        return this.parentEvent.getSender();
     }
 
     public get callId(): string {

src/matrixrtc/MatrixRTCSession.ts

@@ -120,7 +120,7 @@ export class MatrixRTCSession extends TypedEventEmitter<MatrixRTCSessionEvent, M
         callMemberships.sort((a, b) => a.createdTs() - b.createdTs());
         logger.debug(
             "Call memberships, in order: ",
-            callMemberships.map((m) => [m.createdTs(), m.member.userId]),
+            callMemberships.map((m) => [m.createdTs(), m.sender]),
         );
 
         return callMemberships;