JavaScript get textContent via onclick event

Question

There is my table written with php :

$table = "<table>";
$table .=  "<tr><th>ID</th><th>Link</th><th>Öncelik</th><th></th></tr>";
while ($row = mysqli_fetch_assoc($result)) {
    $table .= "<tr>";
    $table .= "<td class='code'>" . $row["Code"] . "</td>";
    $table .= "<td class='link' contenteditable='true' oninput='showSaveButton(this.parentElement)'>" . $row["Link"] . "</td>";
    $table .= "<td class='priority' contenteditable='true' oninput='showSaveButton(this.parentElement)'>" . $row["Priority"] . "</td>";
    $table .= "<td><button onclick='deleteRow(" . $row["Code"] . ")'>Delete</button></td>";
    $table .= "<td><button hidden=true onclick='saveRow(this.parentElement)' class='save-button'>Save</button></td>";
    $table .= "</tr>";
}
$table .= "</table>";
echo $table;

scripts:

function showSaveButton(row) {
    const saveButton = row.querySelector('.save-button');
    saveButton.hidden = false;
}

function saveRow(row) {
    const link = row.querySelector('.link').textContent;
    const priority = row.querySelector('.priority').textContent;;
    const code = row.querySelector('.code').textContent;
    
    const xhr = new XMLHttpRequest();
    const url = "update.php";
    const params = "link=" + encodeURIComponent(link) + "&priority=" + encodeURIComponent(priority) + "&code=" + encodeURIComponent(code);

  xhr.open("POST", url, true);
  xhr.setRequestHeader("Content-type", "application/x-www-form-urlencoded");

  xhr.onreadystatechange = function() {
    if(xhr.readyState == 4 && xhr.status == 200) {
      console.log(xhr.responseText);
    }
  };

  xhr.send(params);

Here is the table picture

When I edit priority or link fields I want the save button to be shown. Then when I click the save button saveRow function should be ran. But I got following error on this line of code:

const link = row.querySelector('.link').textContent; "Cannot read properties of null (reading 'textContent')"

What should I do?

I cut saveRow function context to paste in showSaveButton function but it is working. but in saveRow function Not.