Add room not found view

src/room/GroupCallLoader.jsx

@@ -2,6 +2,8 @@ import React from "react";
 import { useLoadGroupCall } from "./useLoadGroupCall";
 import { ErrorView, FullScreenView } from "../FullScreenView";
 import { usePageTitle } from "../usePageTitle";
+import { isLocalRoomId } from "../matrix-utils";
+import { RoomNotFoundView } from "./RoomNotFoundView";
 
 export function GroupCallLoader({ client, roomId, viaServers, children }) {
   const { loading, error, groupCall } = useLoadGroupCall(
@@ -20,6 +22,10 @@ export function GroupCallLoader({ client, roomId, viaServers, children }) {
     );
   }
 
+  if (error && error.errcode === "M_UNKNOWN" && isLocalRoomId(roomId)) {
+    return <RoomNotFoundView client={client} roomId={roomId} />;
+  }
+
   if (error) {
     return <ErrorView error={error} />;
   }