PHP Notice: Undefined index: from

When writing tests we're intentionally causing sent messages to fail. This PHP notice is generated:

PHP Notice
Undefined index: from

mandrill.module, line 192, mandrill_mailsend()

 watchdog('mandrill', 'Error sending email from %from to %to. @code: @message',
      array(
        '%from' => $message['from'],
        '%to' => $message['to'],
        '@code' => $e->getCode(),
        '@message' => $e->getMessage(),
      ),
      WATCHDOG_ERROR
    );

should be:

    watchdog('mandrill', 'Error sending email from %from to %to. @code: @message',
      array(
        '%from' => $message['from_email'],
        '%to' => $message['to'],
        '@code' => $e->getCode(),
        '@message' => $e->getMessage(),
      ),
      WATCHDOG_ERROR
    );

Patch to follow...