Merge pull request 'Fix untyped/unknown mime file download' (#63) from BordedDev/snek:bugfix/file-download into main

Reviewed-on: #63
Reviewed-by: retoor <retoor@noreply@molodetz.nl>

src/snek/view/channel.py

@@ -114,7 +114,7 @@ class ChannelAttachmentView(BaseView):
             response.headers["Content-Disposition"] = (
                 f'attachment; filename="{channel_attachment["name"]}"'
             )
-            response.headers["Content-Type"] = original_format
+            response.headers["Content-Type"] = original_format or "application/octet-stream"
             return response
 
     async def post(self):