chore: fix psalm issues

Author: roxblnfk

src/Proto/Frame/Smtp.php

@@ -27,9 +27,9 @@ public function __construct(
 
     public static function fromString(string $payload, \DateTimeImmutable $time): static
     {
-        $payload = \json_decode($payload, true, 64, \JSON_THROW_ON_ERROR);
-        /** @var TArrayData $payload */
-        $message = Message\Smtp::fromArray($payload);
+        /** @var TArrayData $data */
+        $data = \json_decode($payload, true, 64, \JSON_THROW_ON_ERROR);
+        $message = Message\Smtp::fromArray($data);
 
         return new self($message, $time);
     }

src/Sender/MailToFileSender.php

@@ -50,10 +50,11 @@ public function send(iterable $frames): void
     /**
      * Get normalized email address for file or directory name.
      *
-     * @param null|non-empty-string $email
+     * @return null|non-empty-string
      */
     private static function normalizeEmail(?string $email): ?string
     {
-        return \trim($email) === '' ? null : \str_replace('@', '[at]', $email);
+        $email = \str_replace('@', '[at]', \trim((string) $email));
+        return $email === '' ? null : $email;
     }
 }