fix mistral streaming with advanced api response

Author: ilvalerione

src/Providers/Mistral/Mistral.php

@@ -13,6 +13,7 @@
 
 use function array_unshift;
 use function json_encode;
+use function is_array;
 
 class Mistral extends OpenAI
 {
@@ -88,7 +89,7 @@ public function stream(array|string $messages, callable $executeToolsCallback):
 
             // Process regular content
             $content = $choice['delta']['content'] ?? '';
-            if (\is_array($content) && $content['type'] === 'text') {
+            if (is_array($content) && $content['type'] === 'text') {
                 $text .= $content['text'];
             } else {
                 $text .= $content;