Fatal error if file size is NULL

Problem/Motivation

If an image widget's file has no size returned from $file->getSize(), a fatal error occurs, causing a "white screen of death".

Steps to reproduce

Proposed resolution

In Drupal core, they added an IF statement to only show the file size span if the size exists. See #3117430: file-link template should not always display file_size. Bartik should do the same in bartik_preprocess_image_widget()

function bartik_preprocess_image_widget(&$variables) {
  if (!empty($variables['element']['fids']['#value'])) {
    $file = reset($variables['element']['#files']);
    if ($size = $file->getSize()) {
      $variables['data']["file_{$file->id()}"]['filename']['#suffix'] = ' <span class="file-size">(' . ByteSizeMarkup::create($size) . ')</span> ';
    }
  }
}

Remaining tasks

User interface changes

API changes

Data model changes