The new window preview overlay requires getting the app icon for a
window from the window tracker when it gets initialized. The window
tracker listens for the same 'window-added' signal on the MetaWorkspace
that the gnome-shell Workspace listens for to add the window preview.
The window tracker however reconnects all its signal handlers whenever
the number of workspaces changes, which means that its signal handlers
get called after the ones in Workspace ones. So by the time the
'window-added' handler in Workspace is called, the window tracker does
not have an app associated with the window.
To fix this ensure that all window related signal handlers in Workspace
are run after the ones in the window tracker.
Fixes https://gitlab.gnome.org/GNOME/gnome-shell/-/issues/3656
Part-of: <https://gitlab.gnome.org/GNOME/gnome-shell/-/merge_requests/1625>
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