bin/tau: update event_graph synced flag when we skip sync

bin/tau/taud/src/main.rs

@@ -396,6 +396,8 @@ async fn realmain(settings: Args, executor: Arc<smol::Executor<'static>>) -> Res
                 }
             }
         }
+    } else {
+        *event_graph.synced.write().await = true;
     }
 
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