Aggiornato Composer

vendor/symfony/mime/Part/Multipart/FormDataPart.php

@@ -58,7 +58,7 @@ final class FormDataPart extends AbstractMultipartPart
         $values = [];
 
         $prepare = function ($item, $key, $root = null) use (&$values, &$prepare) {
-            if (\is_int($key) && \is_array($item)) {
+            if (null === $root && \is_int($key) && \is_array($item)) {
                 if (1 !== \count($item)) {
                     throw new InvalidArgumentException(sprintf('Form field values with integer keys can only have one array element, the key being the field name and the value being the field value, %d provided.', \count($item)));
                 }