fix(telemetry): restore !this.telemetryId guard in OSS _getTelemetryId

Followup to ec5baaba: the previous commit dropped the unset/empty
telemetryId fallback. Restoring it preserves behavioral parity with
pre-PR code in case telemetryId is ever externally mutated to a
falsy value (the type permits "" even if normal flow never sets it).

mem0-ts/src/oss/src/memory/index.ts

@@ -463,6 +463,7 @@ export class Memory {
   private async _getTelemetryId() {
     try {
       if (
+        !this.telemetryId ||
         this.telemetryId === "anonymous" ||
         this.telemetryId === "anonymous-supabase"
       ) {