fix: error while counting attachment when attachment is null

fix error: count(): Argument #1 ($value) must be of type Countable|array, null given

src/Livewire/ChatBox.php

@@ -147,7 +147,7 @@ public function form(Form $form): Form
                             return false;
                         })
                         ->required(function (Get $get) {
-                            if (count($get('attachments')) > 0) {
+                            if (is_array($get('attachments')) && count($get('attachments')) > 0) {
                                 return false;
                             }