only create a filter for sync when not in a guest user session

src/matrix/Session.js

@@ -134,6 +134,15 @@ export class Session {
         return this._callHandler;
     }
 
+    async isGuestSession() {
+        if (typeof this._guestUser !== 'undefined') {
+            return this._guestUser;
+        }
+        const whoami = await this._hsApi.whoami().response();
+        this._guestUser = whoami.is_guest;
+        return Boolean(whoami.is_guest);
+    }
+
     _setupCallHandler() {
         this._callHandler = new CallHandler({
             clock: this._platform.clock,

src/matrix/Sync.js

@@ -175,7 +175,8 @@ export class Sync {
 
     async _syncRequest(syncToken, timeout, log) {
         let {syncFilterId} = this._session;
-        if (typeof syncFilterId !== "string") {
+        let isGuest = await this._session.isGuestSession();
+        if (!isGuest && typeof syncFilterId !== "string") {
             this._currentRequest = this._hsApi.createFilter(this._session.user.id, {room: {state: {lazy_load_members: true}}}, {log});
             syncFilterId = (await this._currentRequest.response()).filter_id;
         }

src/matrix/net/HomeServerApi.ts

@@ -221,6 +221,10 @@ export class HomeServerApi {
         });
     }
 
+    whoami(): IHomeServerRequest {
+        return this._get( "/account/whoami", undefined, undefined, { prefix: CS_V3_PREFIX } );
+    }
+
     createFilter(userId: string, filter: Record<string, any>, options?: BaseRequestOptions): IHomeServerRequest {
         return this._post(`/user/${encodeURIComponent(userId)}/filter`, {}, filter, options);
     }

src/matrix/sessioninfo/localstorage/SessionInfoStorage.ts

@@ -80,5 +80,5 @@ export class SessionInfoStorage implements ISessionInfoStorage {
         sessions = sessions.filter(s => s.id !== sessionId);
         localStorage.setItem(this._name, JSON.stringify(sessions));
     }
-    
+
 }