Upgrade Planner's on_event(...on_gui_selection_state_changed) throws an error when another mod's dropdown changes state. It looks like the fix should be a 1-liner, as similar code exists in the following on_event. Adding the line below seems to fix the problem (again, copied from on_event(...on_gui_elem_changed).

  if not string.find(element.name, "upgrade%-planner%-") then return end

Any chance of getting this fixed? It's affecting our ability to have a game with both this and another mod we want to use.

Fix incoming (for anyone who decides to browse this thread).

https://forums.factorio.com/viewtopic.php?f=92&t=14781&start=260#p310653