In the map editor, while in map view I pressed Q on rail (the pipette tool) and then I got the following error message:

The mod Ultracube: Age of Cube (0.7.0) caused a non-recoverable error.
Please report this error to the mod author.

Error while running event Ultracube::on_player_cursor_stack_changed (ID 37)
No manual crafter.
stack traceback:
    [C]: in function '__index'
    __Ultracube__/scripts/cube_management.lua:147: in function 'player_data'
    __Ultracube__/scripts/cube_management.lua:179: in function 'update_player'
    __Ultracube__/control.lua:186: in function <__Ultracube__/control.lua:185>

The other mods I had on are the following:
Base mod
Elevated Rails
!skins (Skins Factored)
AAI Loaders
AAI Signal Transmission
Better Victory Screen
Bullet Trails
Character mod helper
Disco Science
engineer tf2
Factorio Library
Helmod: Assistant for planning your factory
I, Robot
InformaTron
Krastorio 2 Assets (Ultracube)
LabDansen
Library for mods by Pi-C
Mechanicus (Rebuild)
Milestones
Play Time Display
Pushbutton
Text Plates
Ultracube: Age of Cube