Fix GetValidatorParticipation slot to epoch conversion (#7721)

* Fix current slot conversion

* Update tests

* Use a higher epoch number

beacon-chain/rpc/beacon/validators.go

@@ -469,7 +469,7 @@ func (bs *Server) GetValidatorActiveSetChanges(
 func (bs *Server) GetValidatorParticipation(
 	ctx context.Context, req *ethpb.GetValidatorParticipationRequest,
 ) (*ethpb.ValidatorParticipationResponse, error) {
-	currentSlot := helpers.SlotToEpoch(bs.GenesisTimeFetcher.CurrentSlot())
+	currentSlot := bs.GenesisTimeFetcher.CurrentSlot()
 	currentEpoch := helpers.SlotToEpoch(currentSlot)
 
 	var requestedEpoch uint64

beacon-chain/rpc/beacon/validators_test.go

@@ -1409,6 +1409,37 @@ func TestServer_GetValidatorParticipation_CannotRequestFutureEpoch(t *testing.T)
 	assert.ErrorContains(t, wanted, err)
 }
 
+func TestServer_GetValidatorParticipation_UnknownState(t *testing.T) {
+	db, _ := dbTest.SetupDB(t)
+
+	ctx := context.Background()
+	headState := testutil.NewBeaconState()
+	require.NoError(t, headState.SetSlot(0))
+	epoch := uint64(50)
+	slots := epoch * params.BeaconConfig().SlotsPerEpoch
+	bs := &Server{
+		BeaconDB: db,
+		HeadFetcher: &mock.ChainService{
+			State: headState,
+		},
+		GenesisTimeFetcher: &mock.ChainService{
+			Genesis: time.Now().Add(time.Duration(-1*int64(slots)) * time.Second),
+		},
+		StateGen: stategen.New(db, cache.NewStateSummaryCache()),
+	}
+
+	wanted := "Could not get state: unknown state"
+	_, err := bs.GetValidatorParticipation(
+		ctx,
+		&ethpb.GetValidatorParticipationRequest{
+			QueryFilter: &ethpb.GetValidatorParticipationRequest_Epoch{
+				Epoch: 1,
+			},
+		},
+	)
+	assert.ErrorContains(t, wanted, err)
+}
+
 func TestServer_GetValidatorParticipation_CurrentAndPrevEpoch(t *testing.T) {
 	db, sc := dbTest.SetupDB(t)