mb_strlen() error when saving an upload_or_link url

[swirtSJW]

Current Behavior

Trying to save a dataset with an upload_or_link url fails with the error

This is the result of this line in Drupal Core's FormValidator.php

    if (isset($elements['#maxlength']) && mb_strlen($elements['#value']) > $elements['#maxlength']) {
      $form_state->setError($elements, $this->t('@name cannot be longer than %max characters but is currently %length characters long.', ['@name' => empty($elements['#title']) ? $elements['#parents'][0] : $elements['#title'], '%max' => $elements['#maxlength'], '%length' => mb_strlen($elements['#value'])]));
    }

If the maxlength is set, it will automatically try to validate the string.
It came from this commit
which introduced a default maxlength for many things. I believe the It was missed that upload_or_link should not have a maxlength applied (because it has multiple elements in an array).

Ultimately it is tied to a Drupal core bug
but that solution may be a ways off.

For now we should follow the existing pattern of

    // If a maxlength was set earlier, remove it as it is not allowed here.
    unset($element['#maxlength']);

Expected Behavior

Datasets save without error if they have a upload_or_link value supplied

Steps To Reproduce

1. create a new dataset with a url for the upload
2. save the dataset
3. see error about mb_strlen being unhappy with being fed an array.

Relevant log output (optional)

-

Anything else?