message: chore(sdk-core): improve error handling third party backup
  Ticket:
diff: @@ -295,12 +295,15 @@ export class EcdsaUtils extends baseTSSUtils<KeyShare> {
  isThirdPartyBackup = false
  ): Promise<EncryptedNShare> {
  let backupToBitgoShare: EncryptedNShare;
  - if (isThirdPartyBackup && backupShare.bitGoHeldKeyShares?.keyShares) {
  + if (isThirdPartyBackup) {
  + if (!backupShare.bitGoHeldKeyShares) {
  + throw new Error(`Missing third party backup key shares`);
  + }
  const backupToOtherApiShare = backupShare.bitGoHeldKeyShares.keyShares.find(
  (keyShare) => keyShare.from === 'backup' && keyShare.to === getParticipantFromIndex(recipientIndex)
  );
  if (!backupToOtherApiShare) {
  - throw new Error('Missing Backup to Bitgo key share');
  + throw new Error(`Missing backup to ${getParticipantFromIndex(recipientIndex)} key share`);
  }
  // Since backup is from a third party, it is already encrypted
  backupToBitgoShare = await buildNShareFromAPIKeyShare(backupToOtherApiShare);
  