Operating system: Windows-10-10.0.17134 64 Bits
Graphics card: GeForce GTX 1060/PCIe/SSE2 NVIDIA Corporation 4.5.0 NVIDIA 419.17
Broken: version: 2.80 (sub 54), branch: master, commit date: 2019-04-05 16:50, hash: rB2219f28a68b6
Short description of error
Outliner light gray pre-select highlight persists after the mouse leaves the Outliner region.
Exact steps for others to reproduce the error
Move the mouse over the Outliner, observing the light gray pre-select highlight tracks the mouse position indicating which thing the mose is potentially targeting. Now move the mouse to the left out of the Outliner region and see that the highlight remains, now fixed in place, even though it's meaningless at that point.
This complicates the already complicated Outliner view by making it look like there's some other state involved like the blue Outliner-selected highlight bar.
The pre-select highlight should be removed when the mouse leaves the Outliner. In my humble opinion anyway :)