Bug Fix:
- Sometimes a group didn't collapse despite all tabs being unloaded.

New Feature:
- When unloading a whole group of tabs, the group is automatically collapsed.
- When unloading the last active tab in a group, the group is automatically collapsed.

Bug Fix:
- When unloading tabs, browser would switch to closest tab, regardless of whether it was active or not. The fix makes it switch to the closest active tab instead.