Extension not added to download when saving it under a different name

[DonaldDuck313]

OS
Windows

Gmail Desktop Version
2.25.3.0

Describe the bug
When I download a file and choose a different name than the original name, the extension isn't automatically added to the file. For example if I download a file called "somefile.pdf" and decide to name it "test", the ".pdf" isn't added automatically.

Steps to reproduce the behavior

1. Find an email with an attachment that contains an extension. For example, assume the attachment is called "somefile.pdf".
2. Download the attachment, you will see a Save As dialog where you get to choose the name of the file. By default the name is "somefile", ax expected.
3. Call it something else, for example "test".
4. Click "Save".
5. Go to the folder where you saved it in Windows Explorer. The file won't be named "test.pdf" as expected, but just "test" without an extension.

Expected behavior
The extension should be added automatically, for example if I try to save a pdf file as "test", it should automatically be named "test.pdf".

Media