The iOS messaging that causes iMessages to crash has caused people a lot of headaches and searching for fixes. The unicode message can cause the message app to restart, and can cause the iPhone to even restart. Apple hasn’t fixed the issue, but is offering a work around for its users.
The work around isn’t elegant but makes sure users can continue to send and receive messages. You’ll have to ask siri to read unread messages to you. Once the message is read you’ll need siri to reply to the Unicode message. Then the message app should open and work. You’ll need to then delete the message thread so the message doesn’t cause any more issues.
Apple should offer a fix in the near future and prevent the message from causing as much issues as it does. The work around should help in the mean time, but we can hope Apple pushes an update out quickly. Tell us in the comments below if anyone has sent you the message and how you managed to fix it.