fix: Email attachments created with empty filename (#10420)

- We observed in prod for certain emails active storage blob objects
were getting created with empty file name. The conversations further
causes conversation and filter pages to break. This change will fix the
mentioned issue.

fixes:
https://linear.app/chatwoot/issue/CW-3331/missing-file-name-for-some-of-the-uploads-for-emails

---------

Co-authored-by: Pranav <pranavrajs@gmail.com>

app/presenters/mail_presenter.rb

@@ -77,7 +77,7 @@ class MailPresenter < SimpleDelegator
     mail.attachments.map do |attachment|
       blob = ActiveStorage::Blob.create_and_upload!(
         io: StringIO.new(attachment.body.to_s),
-        filename: attachment.filename,
+        filename: attachment.filename.presence || "attachment_#{SecureRandom.hex(4)}",
         content_type: attachment.content_type
       )
       { original: attachment, blob: blob }