Skip request when there are no validators

shared/services/beacon/client/std-http-client.go

@@ -313,6 +313,13 @@ func (c *StandardHttpClient) GetValidatorStatuses(pubkeys []types.ValidatorPubke
 
 // Get whether validators have sync duties to perform at given epoch
 func (c *StandardHttpClient) GetValidatorSyncDuties(indices []string, epoch uint64) (map[string]bool, error) {
+	// Map to store results
+	validatorMap := make(map[string]bool)
+
+	// Return if there are not validators to check
+	if len(indices) == 0 {
+		return validatorMap, nil
+	}
 
 	// Perform the post request
 	responseBody, status, err := c.postRequest(fmt.Sprintf(RequestValidatorSyncDuties, strconv.FormatUint(epoch, 10)), indices)
@@ -329,9 +336,6 @@ func (c *StandardHttpClient) GetValidatorSyncDuties(indices []string, epoch uint
 		return nil, fmt.Errorf("Could not decode validator sync duties data: %w", err)
 	}
 
-	// Map the results
-	validatorMap := make(map[string]bool)
-
 	for _, index := range indices {
 		validatorMap[index] = false
 		for _, duty := range response.Data {