Index: src/wp-includes/taxonomy.php
===================================================================
--- src/wp-includes/taxonomy.php	(revision 36269)
+++ src/wp-includes/taxonomy.php	(working copy)
@@ -4423,7 +4423,9 @@
 			$ancestors = get_ancestors( $term->term_id, $taxonomy, 'taxonomy' );
 			foreach ( (array)$ancestors as $ancestor ) {
 				$ancestor_term = get_term($ancestor, $taxonomy);
-				$hierarchical_slugs[] = $ancestor_term->slug;
+				if ( $ancestor_term ){
+					$hierarchical_slugs[] = $ancestor_term->slug;
+				}
 			}
 			$hierarchical_slugs = array_reverse($hierarchical_slugs);
 			$hierarchical_slugs[] = $slug;