message: Don't register token-to-usd helper until a non-zero amount is present
diff: @@ -6,6 +6,7 @@ import {
  convertibleSymbols,
  ConvertibleSymbol,
  } from '@cardstack/web-client/utils/token';
  +import { toBN } from 'web3-utils';
  type TokenToUsdHelperParams = [ConvertibleSymbol, BN];
  @@ -30,8 +31,12 @@ class TokenToUsdHelper extends Helper {
  }
  this.symbol = symbol;
  this.amount = amount;
  + if (amount?.gt(toBN(0))) {
  this.tokenToUsdService.register(this);
  return this.tokenToUsdService.toUsdFrom(symbol, amount);
  + } else {
  + return '0.00';
  + }
  }
  willDestroy() {
  