Fixes the problem reported here:
When using the Outliner in "View Layer" mode the active and selected objects are shown specially by having their icons have a background circle that is painted in orange and red (depends on theme).
But when viewing in "Scene" mode however, you only see a black circle for the active object, whether selected or not. So select an object then deselect all and you will still see that object with black circle. But you never see any with orange and red like you do as when in View Layer mode
Basically they way that "is_selected" is evaluated in there doesn't work when viewing as scene. This patch fixes that. The following capture shows the current behavior on left, the fixed behavior on right.
Note this patch does nothing but fix this one small thing, so just a one-line change.
Larger changes to outliner remain here and I will incorporate this fix into that patch as well.