fix: add defensive check for mail_id in download view (#114)

The $getState() function may return a string instead of a model in some
contexts. This fix adds a type check and only renders the download button
when a valid attachment object with mail_id is available.

Fixes #69

Co-authored-by: Claude Opus 4.5 <noreply@anthropic.com>

Author: Baspa

resources/views/mails/download.blade.php

@@ -1,8 +1,15 @@
+@php
+    $attachment = $getState();
+    $mailId = is_object($attachment) ? $attachment->mail_id : null;
+@endphp
+
+@if($mailId && $attachment)
 <a type="button"
     href="{{ route('filament.' . Filament\Facades\Filament::getCurrentPanel()->getId() . '.mails.attachment.download', [
         'tenant' => Filament\Facades\Filament::getTenant(),
-        'mail' => $getState()->mail_id,
-        'attachment' => $getState()->id,
-        'filename' => $getState()->filename,
+        'mail' => $mailId,
+        'attachment' => $attachment->id,
+        'filename' => $attachment->filename,
     ]) }}"
     class="rounded-md bg-white px-3.5 py-2.5 text-sm font-semibold cursor-pointer text-gray-900 shadow-sm ring-1 ring-inset ring-gray-300 hover:bg-gray-50">Download</a>
+@endif