| Fix the following issue: | |
| ## RUM events being ingested without a `sessionId` | |
| While looking at the RUM events our app sends to the Datadog intake, I noticed a non-trivial number of them are missing a `sessionId` (the field is just absent / undefined on the event). These same events still have a view id and look otherwise valid, they just have no session attached, which makes them useless for session-level analysis. | |
| After some digging I managed to reproduce it with the following setup: | |
| 1. Open our app in two tabs, both initialized with the browser RUM SDK. The session is initially **not** sampled / not tracked. | |
| 2. Wait for the session to expire. | |
| 3. In tab A, do something that causes the SDK to renew the session, and this time the new session lands in the *tracked* bucket. | |
| 4. Switch to tab B (do **not** interact with it — don't click, don't navigate, just let background things like XHRs, long tasks, errors etc. happen). | |
| Tab B keeps sending RUM events to the intake, and those are the ones showing up without a `sessionId`. Tab B never had a chance to react to the renewed session — from its point of view it's still on the last view of the now-expired session — yet events from it keep flowing through. | |
| I'd expect the SDK to simply **not send** RUM events when it can't attach them to a real session. A tab that hasn't seen any actual user interaction since the session was renewed shouldn't be silently producing orphan events in the backend. |