Describe the bug
I believe backups are sometimes being run twice when using scheduled backups.

This sometimes results in Vorta reporting that a backup did not complete successfully (one of the two duplicate scheduled backups fails).
This sometimes results in Vorta creating two backups for the same scheduled backup - these can be seen in the 'Archives' tab .

In addition to the above issues, the value for 'Next Backup' in the 'Schedule' tab does not appear to be updated - clearly this is fairly minor.

To Reproduce
Steps to reproduce the behavior:

1. Use the 'Backup every...' facility in the Schedule tab

Environment (please complete the following information):

• OS: Arch Linux
• Vorta version: Vorta 0.7.8
• Installed from: Arch AUR - vorta-git. (pacman -Q vorta-git outputs vorta-git r565.fba6a2f-1)
• Borg: 1.1.17

Additional context
I previously used the vorta AUR package. However, I was affected by #1083 and switched to using vorta-git. As such I am running Vorta built from the latest commit - currently fba6a2f.

Vorta logs HERE

If you need me to run Vorta in debug mode please let me know (and tell me how to do it!). If you need any further info please let me know.