Allowed for missing genre

src/NodeBuilder.php

@@ -59,6 +59,7 @@ final class NodeBuilder {
       ];
     }
     $genre = $term_mappings[$contents['type']] ?? NULL;
+    if ($genre) {
       $terms = $this->entityTypeManager->getStorage('taxonomy_term')->loadByProperties([
         'name' => $genre,
         'vid' => 'genre',
@@ -67,6 +68,8 @@ final class NodeBuilder {
         $genre = reset($terms);
       }
 
+    }
+
     // Build new node.
     $new_node = Node::create([
       $field_settings['title'] => htmlspecialchars_decode($contents['title'][0]),
@@ -75,7 +78,6 @@ final class NodeBuilder {
       $field_settings['contributors'] => $typed_relations,
       $field_settings['publisher'] => $contents['publisher'] ?? '',
       $field_settings['doi'] => $doi,
-      $field_settings['genre'] => $genre->id(),
       $field_settings['issue'] => $contents['issue'] ?? '',
       $field_settings['volume'] => $contents['volume'] ?? '',
       $field_settings['date_issued'] => $contents['created']['date-parts'][0][0] ?? '',