Umlauts break attachment names ("Unnamed Attachment")

Description

Some attachments loose their name, i.e. get renamed to Unnamed Attachment. It seems to affect attachments that contain special characters like German Umlauts (äöü)

To Reproduce…

Steps to reproduce the behavior:

  1. receive an attachment with a special character luie a German Umlaut (äöü)

Expected Behavior

Name shows up as given

Setup

  • OS and Version: Ubuntu Linux 25.04
    • Installation Method: installer
  • Mailspring Version: 1.15.1