Fix possible deadloop in beacon (#6451)

## Motivation

I found a problem in the beacon protocol where if the node wakes up from sleep or syncs its clock via NTP at the wrong moment the go routine running the beacon protocol might end up in a deadloop without ever recovering.

CHANGELOG.md

@@ -6,7 +6,6 @@ See [RELEASE](./RELEASE.md) for workflow instructions.
 
 ### Improvements
 
-* [#6431](https://github.com/spacemeshos/go-spacemesh/pull/6431) Fix db-allow-schema-drift handling
 * [#6408](https://github.com/spacemeshos/go-spacemesh/pull/6408) Prevent empty DB connection pool by freeing connections
   upon errors during DB operations. This mostly fixes issues when a node is under heavy load from the API.
 
@@ -16,6 +15,10 @@ See [RELEASE](./RELEASE.md) for workflow instructions.
 * [#6422](https://github.com/spacemeshos/go-spacemesh/pull/6422) Further improved performance of the proposal building
   process to avoid late proposals.
 
+* [#6431](https://github.com/spacemeshos/go-spacemesh/pull/6431) Fix db-allow-schema-drift handling
+
+* [#6451](https://github.com/spacemeshos/go-spacemesh/pull/6451) Fix a possible deadloop in the beacon protocol.
+
 ## v1.7.6
 
 ### Upgrade information

api/grpcserver/v2alpha1/node_test.go

@@ -23,7 +23,8 @@ func TestNodeService_Status(t *testing.T) {
 		timesync.WithLayerDuration(layerDuration),
 		timesync.WithTickInterval(1*time.Second),
 		timesync.WithGenesisTime(time.Now()),
-		timesync.WithLogger(zaptest.NewLogger(t)))
+		timesync.WithLogger(zaptest.NewLogger(t)),
+	)
 	require.NoError(t, err)
 	defer clock.Close()
 

beacon/beacon.go

@@ -729,16 +729,16 @@ func (pd *ProtocolDriver) listenEpochs(ctx context.Context) {
 				pd.logger.Debug("time sync detected, realigning Beacon")
 				continue
 			}
+			epoch := current.GetEpoch()
+			layer = epoch.Add(1).FirstLayer()
 			if !current.FirstInEpoch() {
 				continue
 			}
-			epoch := current.GetEpoch()
-			layer = epoch.Add(1).FirstLayer()
 
 			pd.setProposalTimeForNextEpoch()
 			pd.logger.Info("processing epoch", zap.Uint32("epoch", epoch.Uint32()))
 			pd.eg.Go(func() error {
-				_ = pd.onNewEpoch(ctx, epoch)
+				pd.onNewEpoch(ctx, epoch)
 				return nil
 			})
 		}