The mod GUI Unifyer (1.8.0) caused a non-recoverable error.
Please report this error to the mod author.

Error while running event GUI_Unifyer::on_research_finished (ID 18)
GUI_Unifyer/control.lua:175: attempt to index field 'factory_camera_toggle_button' (a nil value)
stack traceback:
GUI_Unifyer/control.lua:175: in function 'update_factorissimo'
GUI_Unifyer/control.lua:295: in function <GUI_Unifyer/control.lua:291>

This crash took place when a research finished.

Getting an extremely similar error. Except it happens on loading a save. I literally saved, went to change some settings, ended up not doing that, updated the mod while I'm at it, and couldn't load back in.

The mod GUI Unifyer (1.8.0) caused a non-recoverable error.
Please report this error to the mod author.

Error while running event GUI_Unifyer::on_configuration_changed
GUI_Unifyer/control.lua:175: attempt to index field 'factory_camera_toggle_button' (a nil value)
stack traceback:
GUI_Unifyer/control.lua:175: in function 'update_factorissimo'
GUI_Unifyer/control.lua:288: in function <GUI_Unifyer/control.lua:283>

Ah ! It should be fixed now ! I was out for the evening, then steam crashed and locked me out of my factorio mods account! So sorry for the crash.

Don't you worry. Thank you for the quick response and the generally awesome work you do here!

That's very kind, thank you : )

FWIW, to avoid any future bits, maybe check game.active_mods['mod-name'] to see if the mod is present and loaded at runtime?

Thank you~