add null guards in bulk create nodes use case

app/Node/UseCases/BulkCreateNodes.php

@@ -2,6 +2,7 @@
 
 namespace App\Node\UseCases;
 
+use App\Exceptions\BadRequestException;
 use App\Node\CreateNodeDto;
 use App\Node\Node;
 use App\Node\NodeRepository;
@@ -21,6 +22,22 @@ class BulkCreateNodes
      */
     public function execute(BulkCreateNodesRequest $request): array
     {
+        if ($request->textId === null) {
+            throw new BadRequestException('textId is required');
+        }
+
+        if ($request->parentNodeId === null) {
+            throw new BadRequestException('parentNodeId is required');
+        }
+
+        if ($request->titlePrefix === null) {
+            throw new BadRequestException('titlePrefix is required');
+        }
+
+        if ($request->count === null) {
+            throw new BadRequestException('count is required');
+        }
+
         $text = $this->textRepo->find($request->textId);
         if ($text === null) {
             throw new DomainException("Text with id: {$request->textId} doesnt exist");