[Private] Undefined property: WP_Error::$name

Hello,
I've created a custom taxonomy "birthplace" with hierarchical terms like "Australia" and "Sydney".
In the builder I've set in the taxonomies "Term parent" and "Term title".
In the index.php of twentytwenty-theme I use this shortcode: 'echo do_shortcode("[breadcrumb]");'

Unfortunately I got an PHP-error in the Query Monitor, when loading the page example.de/birthplace/australia/ :

Undefined property: WP_Error::$name.
Details:
wp-content/plugins/breadcrumb/includes/functions-hooks.php:961
breadcrumb_permalink_term_parent()
wp-includes/class-wp-hook.php:307
apply_filters('breadcrumb_permalink_term_parent')
wp-content/plugins/breadcrumb/includes/functions-hooks.php:188
breadcrumb_items_override_permalinks()
wp-includes/class-wp-hook.php:307
apply_filters('breadcrumb_items_array')
wp-content/plugins/breadcrumb/templates/breadcrumb/breadcrumb-hook.php:10
breadcrumb_main_items()
wp-includes/class-wp-hook.php:307
do_action('breadcrumb_main')
wp-content/plugins/breadcrumb/includes/class-shortcodes.php:47
class_breadcrumb_shortcodes->breadcrumb_display()
wp-includes/shortcodes.php:356
do_shortcode_tag()
Unbekannter Ort
preg_replace_callback()
wp-includes/shortcodes.php:228
do_shortcode()
wp-content/themes/twentytwenty-child/index.php:575

When I call the child-term example.de/birthplace/australia/sydney/, the error-message disappears!

How can I solve this problem?

Thank you in advance for your help!
Andreas