If any light source is deleted, and a single light has its visibility state changed in LightMixer, all the other lights in the scene that were invisible turn visible

If any light source is deleted, and a single light has its visibility state changed in LightMixer, all the other lights in the scene that were invisible turn visible. The behavior only shows after deleting one of the listed lights.
I've reproduced this behavior on 5.6 and 5.7 (CL44372627).

On a blank project, create a new Empty Level
Add a few PointLights
Open Window>LightMixer
Toggle their visibility on the LightMixer window, so all of them are invisible
At this point, toggling a single light visibility will affect only said light
Now delete one of the lights
Toggle the visibility of one of the other lights

Expected result: only the toggled light should have it's state toggled
Actual result: all of the other invisible lights become visible. Toggling the same light won't toggle all lights - it only shows this behavior the first time, and from invisible to visible.