fix: return null instead of throwing exception for GraphQL query operation when item not found

Author: Roman Skoropadsky

src/GraphQl/State/Provider/ReadProvider.php

@@ -21,6 +21,7 @@
 use ApiPlatform\Metadata\CollectionOperationInterface;
 use ApiPlatform\Metadata\GraphQl\Mutation;
 use ApiPlatform\Metadata\GraphQl\Operation as GraphQlOperation;
+use ApiPlatform\Metadata\GraphQl\Query;
 use ApiPlatform\Metadata\GraphQl\QueryCollection;
 use ApiPlatform\Metadata\GraphQl\Subscription;
 use ApiPlatform\Metadata\IriConverterInterface;
@@ -68,6 +69,10 @@ public function provide(Operation $operation, array $uriVariables = [], array $c
                 $item = null;
             }
 
+            if ($operation instanceof Query && null === $item) {
+                return $item;
+            }
+
             if ($operation instanceof Subscription || $operation instanceof Mutation) {
                 if (null === $item) {
                     throw new NotFoundHttpException(sprintf('Item "%s" not found.', $args['input']['id']));