错误 - 未捕获的类型错误：无法读取 null 的属性“选项”

我正在尝试将选择值放入变量中，但它给了我一个错误 - 未捕获的类型错误：无法读取 null 的属性“选项”，html 代码：

<select onchange="transaction()" id="сurrencyMain">

      <option value="0">Bitcoin</option>
      <option value="1023">Ether</option>
      <option value="1223">Bitcoin Cash</option>

    </select>

js代码：

function transaction() {
    var currencyMain = document.getElementById('currencyMain');
       var  addres_field = document.getElementById('address-field');
       var amount_bit = document.getElementById('amount-bit');
       var amount_rub = document.getElementById('amount-rub');
       var  description = document.getElementById('description');
       var transaction_fee = document.getElementById('transaction_fee');
       var  currencyTab = document.getElementById('currencyTab');

        var price = 0;
        price += parseInt(currencyMain.options[currencyMain.selectedIndex].value);
        currencyTab.innerHTML = price;
}