If the new base_url field is left blank there are errors like:
Deprecated function: file_exists(): Passing null to parameter #1 ($filename) of type string is deprecated in Drupal\migrate\Plugin\migrate\process\FileCopy->transform() (line 134 of /var/www/html/core/modules/migrate/src/Plugin/migrate/process/FileCopy.php)
Message Deprecated function: preg_match(): Passing null to parameter #2 ($subject) of type string is deprecated in Drupal\Core\StreamWrapper\StreamWrapperManager::getScheme() (line 294 of /var/www/html/core/lib/Drupal/Core/StreamWrapper/StreamWrapperManager.php)
Deprecated function: basename(): Passing null to parameter #1 ($path) of type string is deprecated in Drupal\migrate\Plugin\migrate\process\Callback->transform() (line 103 of /var/www/html/core/modules/migrate/src/Plugin/migrate/process/Callback.php)
This is a shortcoming of ✨ Import permalink as URL paths RTBC patch.
Upload an xml file without adding the site basename,
Bypass the path alias generator steps if blank.
None.
Active
3.0
Code
Issue #3488554: base_url should be bypassed if blank
Automatically closed - issue fixed for 2 weeks with no activity.