Incorrect error handling when starting multiple Qube Backup sessions

[jmynes]

Qubes OS release

Qubes OS 4.2

Brief summary

Nothing in the UI indicates that users cannot run two separate Qube Backups of different qubes, either to one or more target qubes. e.g. A user has a qube named test1, and a qube named test2, and wants to make two separate backups, instead of one bundle

Attempting to do this will allow users to advance through the menus, but at the last moment, display an error message:

ERROR: This backup is already in progress! Cancel it or wait until it finishes.

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This error message implies that the user has accidentally selected the same qube twice, rather than test1 and test2, as described in the example above. This is further confusing because it spawns a second window and progress bar, tracking the progress from the first backup, test1

When this backup finishes, the initial window will say Backup finished., but the second window reports Backup error., despite referring to the same backup task:

Steps to reproduce

1. Backup any selection of qube(s)
2. Before Backup 1 completes, Attempt to backup any second selection of qube(s), ideally(?) with no overlap

Expected behavior

Two or more concurrent backups should either be possible, or an error message should prevent users from attempting to start a second concurrent backup

Actual behavior

Backup messaging is confusing, implies backup may have become malformed

Additional information

No response