Prevent $mailer being reset when testing mailables that implement ShouldQueue (#42695)

Author: JayBizzle

src/Illuminate/Support/Testing/Fakes/MailFake.php

@@ -363,12 +363,13 @@ public function send($view, array $data = [], $callback = null)
 
         $view->mailer($this->currentMailer);
 
-        $this->currentMailer = null;
 
         if ($view instanceof ShouldQueue) {
             return $this->queue($view, $data);
         }
 
+        $this->currentMailer = null;
+
         $this->mailables[] = $view;
     }