Also reported here: https://github.com/Nexela/PickerBeltTools/issues/14

19078.994 Error MainLoop.cpp:1183: Exception at tick 77207085: The mod Picker Belt Tools caused a non-recoverable error.
Please report this error to the mod author.

Error while running event PickerBeltTools::on_selected_entity_changed (ID 52)
PickerBeltTools/scripts/belt-highlight.lua:418: attempt to get length of local 'input' (a nil value)
stack traceback:
PickerBeltTools/scripts/belt-highlight.lua:418: in function <PickerBeltTools/scripts/belt-highlight.lua:364>
(...tail calls...)
PickerBeltTools/scripts/belt-highlight.lua:534: in function <PickerBeltTools/scripts/belt-highlight.lua:364>
(...tail calls...)
PickerBeltTools/scripts/belt-highlight.lua:614: in function 'read_belts'
PickerBeltTools/scripts/belt-highlight.lua:1060: in function 'highlight_belts'
PickerBeltTools/scripts/belt-highlight.lua:1113: in function 'handler'
stdlib/stdlib/event/event.lua:313: in function 'pcall'
stdlib/stdlib/event/event.lua:333: in function 'dispatch_event'
stdlib/stdlib/event/event.lua:411: in function <stdlib/stdlib/event/event.lua:367

Same error here i think
https://i.imgur.com/wNtxazi.png

Fwiw, he commented on github that they have a fix, but for some reason just closed the ticket instead of actually releasing anything:

https://github.com/Nexela/PickerBeltTools/issues/14

A bugfix doesn't exactly relate to an instant release, as can be seen by the release schedule of factorio.

We are going to get the bugfix out.

nice looking forward for the bugfix

You can patch the files by hand in the meantime, if you like. The actual fix is included in the commit here:

https://github.com/Nexela/PickerBeltTools/commit/382f76120a5876ba7d2f999412553a1c1753875a