'Computer' sidebar is not updated correctly when removeable drives are un/mounted

[ronso0]

Bug Description

here and below https://mixxx.zulipchat.com/#narrow/stream/109122-general/topic/linux.3A.20mounting.20drive.20after.20starting.20mixxx/near/423779346

Seems to be a model update issue:
When I unmount the drive, the child is removed but the 'user' item (parent) still has the '>' icon indicating children.
Explicit repaint doesn't fix it

And some extra debug stuff tells me Mixxx does see the newly mounted drive directory.
But it's currently not able to expand the item, or doesn't consider it expandable in the first place.

Issue occurs with 2.4

Version

No response

OS

No response