UI: seemingly false report of 'snapshot device not selected'

[LinuxOnTheDesktop]

Describe the bug
A clear and concise description of what the bug is.

To Reproduce
Perhaps simply:

• set up the program to use rsync;
• configure a schedule.

Expected behavior
I do not expect to be told that no snapshot device is selected when such a device is selected. But perhaps that is not what the application mean to convey - in which case, what it does mean to convey should be made clear.

Screenshots

System:

• Linux Distribution Name and Version: Mint 20.1
• Desktop: Cinnamon
• Application Version: v.20.11.1