Notice: Array to string conversion - line 218 of src/Type/CDNBase.php

I am seeing a flood of these PHP notices in my Recent Log Messages:

Notice: Array to string conversion in Drupal\libraries_cdn\Type\CDNBase->Drupal\libraries_cdn\Type\{closure}() (line 218 of .../libraries_cdn/src/Type/CDNBase.php).

They occur on every pageload many many times.

Upon closer inspection, it looks like the $v variable is sometimes a string and sometimes an array. The code on line 218 assumes it is always a string (it concatenates it to another string). Here's what the code looks like, for quick reference:

  /**
   * {@inheritdoc}
   */
  public function convertFiles(array $files, $version) {
    $url = $this->getURL(__FUNCTION__);
    return array_map(function($v) use ($url, $version) {
      return sprintf($url, $this->getLibrary(), $version) . $v;
    }, $files);
  }

If I dpm($v); on my site, it looks like sometimes it is a string that contains the name of a library file to load, and other times it is an array in the following form:

array(
  'name' => 'ol-debug.js',
  'integrity' => 'sha256-Ye0VjmSihS0WHaLTveqwKv4CsaBakp84TGIpQUK/ef4=',
)

I then searched (via grep) for "integrity" in libraries_cdn and openlayers modules, but neither turned up any occurrences. So I'm not sure where that "integrity" array key is coming from.

I tried simply changing line 218 to:

return sprintf($url, $this->getLibrary(), $version) . $v['name'];

... That fixes most of the notices, but creates new ones:

Warning: Illegal string offset 'name' in Drupal\libraries_cdn\Type\CDNBase->Drupal\libraries_cdn\Type\{closure}() (line 218 of .../libraries_cdn/src/Type/CDNBase.php).

That's because $v is only SOMETIMES an array - and other times it is a string, as expected.

So I'm not sure what's up! Any ideas?