fix sse event failure

Author: eserilev

beacon_node/beacon_chain/src/beacon_chain.rs

@@ -2049,6 +2049,17 @@ impl<T: BeaconChainTypes> BeaconChain<T> {
                             }
                         }
                     }
+
+                    if event_handler.has_attestation_subscribers() {
+                        let current_fork = self
+                            .spec
+                            .fork_name_at_slot::<T::EthSpec>(v.attestation().data().slot);
+                        if !current_fork.electra_enabled() {
+                            event_handler.register(EventKind::Attestation(Box::new(
+                                v.attestation().clone_as_attestation(),
+                            )));
+                        }
+                    }
                 }
                 metrics::inc_counter(&metrics::UNAGGREGATED_ATTESTATION_PROCESSING_SUCCESSES);
             },