fix(CommitCommand): Replace null with empty string in message

- Replace the null value with an empty string in the message
- This change ensures that the message structure remains consistent and avoids issues with null values
- Improves overall handling of commit messages in the application

app/Commands/CommitCommand.php

@@ -116,7 +116,7 @@ function ($attempts) use ($cachedDiff, $type): string {
                     return $content;
                 })
                 ->tap(function (Collection $message): void {
-                    $message = $message->put('', null)->sortKeysUsing(static function (string $a, string $b): int {
+                    $message = $message->put('', '')->sortKeysUsing(static function (string $a, string $b): int {
                         $rules = ['subject', '', 'body'];
 
                         return array_search($a, $rules, true) <=> array_search($b, $rules, true);