I think I had bad timing with space exploration (if I'm reading this right, a spaceship was taking off or landing when I tried to highlight the belts)

The mod Space Exploration (0.6.90) caused a non-recoverable error.
Please report this error to the mod author.

Error while running event space-exploration::on_tick (ID 0)
The mod Belt Visualizer (1.1.1) caused a non-recoverable error.
Please report this error to the mod author.

Error while running event belt-visualizer::on_entity_cloned (ID 123)
belt-visualizer/control.lua:119: attempt to index local 'entity' (a nil value)
stack traceback:
belt-visualizer/control.lua:119: in function 'highlightable'
belt-visualizer/control.lua:138: in function <belt-visualizer/control.lua:135>
stack traceback:
[C]: in function 'clone_brush'
space-exploration/scripts/spaceship-clone.lua:276: in function 'clone'
space-exploration/scripts/spaceship.lua:1809: in function 'spaceship_tick'
space-exploration/scripts/spaceship.lua:2021: in function 'callback'
space-exploration/scripts/event.lua:15: in function <space-exploration/scripts/event.lua:13>

Ah, this is actually a small error on my part. I incorrectly assumed that the event for cloning an entity used a field called "entity" for the new created entity, however it is called "destination" instead. Fixed in 1.1.2