Don't pass async runner if no external signer public key sources

Author: courtneyeh

validator/client/src/main/java/tech/pegasys/teku/validator/client/ValidatorClientService.java

@@ -424,7 +424,10 @@ private static ValidatorLoader createValidatorLoader(
         HttpClientExternalSignerFactory.create(validatorConfig);
     final Optional<AsyncRunner> maybeAsyncRunner =
         Optional.ofNullable(
-            validatorConfig.validatorExternalSignerPublicKeysRetryEnabled() ? asyncRunner : null);
+            !validatorConfig.getValidatorExternalSignerPublicKeySources().isEmpty()
+                    && validatorConfig.validatorExternalSignerPublicKeysRetryEnabled()
+                ? asyncRunner
+                : null);
     return ValidatorLoader.create(
         config.getSpec(),
         validatorConfig,