bug(files): Send Files button from Share Files should be disabled if no user is selected

[luisecm]

Description:
If you open the share files modal and select any file(s), but you do not select any user to share, you still can click the Send Files button. However no action is performed and modal is disabled.
However, if you go to share files, unselect the file you will see the send files button blocked. So I believe the button behavior should be consistent and be unclickable unless you can actually send files

Environment:
MacOS

Prerequisites:
Account created with friends and files uploaded

Steps to reproduce:

1. Login with account with friends
2. Go to files
3. Right click on a file
4. Select Share Files
5. Make sure at least one file is selected and that no users are selected
6. You will see the Send Files button can be clicked. Click on it and modal will be gone

Video:
https://github.com/Satellite-im/Uplink/assets/35935591/fc6fa225-d9be-43da-a189-0d7188c34571