Prevent the federate which doesn't have any upstream federates to adv…

…ance its tag above stop requested tag

src/core/federation.ts

@@ -1036,6 +1036,9 @@ export class FederatedApp extends App {
         // Otherwise, set the tagBarrier using the greated TAG.
         if (this.stopRequestInfo.state === StopRequestState.SENT) {
             tagBarrier = this.stopRequestInfo.tag;
+            if (this.upstreamFedIDs.length === 0 && tagBarrier.isSmallerThan(nextEvent.tag)) {
+                return false;
+            }
         } else {
             tagBarrier = this._getGreatestTimeAdvanceGrant();
         }