Fix #1818: explorer keep previous error until refresh in cardano tx certification modal

This was simply due to the error not being set to its default state when
opening the modal.

Author: Alenar

mithril-explorer/src/components/CertifyCardanoTransactionsModal/index.js

@@ -45,6 +45,7 @@ export default function CertifyCardanoTransactionsModal({
     setIsCertificateChainValid(true);
     setCertificate(undefined);
     setCurrentStep(validationSteps.ready);
+    setCurrentError(undefined);
 
     if (transactionHashes?.length > 0) {
       fetchGenesisVerificationKey(currentAggregator)