else {
  return this.getAccounts().pipe(
    tap((accounts: string[]) => {
      if (accounts.length === 0) { throw new Error(‘No accounts available’); }
      }),
    map((accounts: string[]) => accounts[0]),
    tap((account: string) => this.web3.eth.defaultAccount = account),
    catchError((err: Error) => of(err))
  );
}