refactor(notifications): Improve transactional email settings handling

- Replace `! $type` checks with `blank($type)` for consistency
- Modify email settings configuration to handle null/disabled states
- Ensure proper fallback and configuration of email providers

app/Notifications/Channels/EmailChannel.php

@@ -50,11 +50,9 @@ class EmailChannel
 
         if ($emailSettings->use_instance_email_settings) {
             $type = set_transanctional_email_settings();
-            if (! $type) {
+            if (blank($type)) {
                 throw new Exception('No email settings found.');
             }
-            config()->set('mail.default', $type);
-
             return;
         }
 

app/Notifications/Channels/TransactionalEmailChannel.php

@@ -35,7 +35,7 @@ class TransactionalEmailChannel
     private function bootConfigs(): void
     {
         $type = set_transanctional_email_settings();
-        if (! $type) {
+        if (blank($type)) {
             throw new Exception('No email settings found.');
         }
     }

app/Notifications/TransactionalEmails/ResetPassword.php

@@ -3,6 +3,7 @@
 namespace App\Notifications\TransactionalEmails;
 
 use App\Models\InstanceSettings;
+use Exception;
 use Illuminate\Notifications\Messages\MailMessage;
 use Illuminate\Notifications\Notification;
 
@@ -35,8 +36,8 @@ class ResetPassword extends Notification
     public function via($notifiable)
     {
         $type = set_transanctional_email_settings();
-        if (! $type) {
-            throw new \Exception('No email settings found.');
+        if (blank($type)) {
+            throw new Exception('No email settings found.');
         }
 
         return ['mail'];