Looks like this is where incubators comes from, it's in globals.gd
Viewing post in Aric's Expansion Rebred
yeah all of the resources tracked by the game (food, gold, etc.) are in resources in the globals file.
i noticed today if i bought an incubator then tried to use it i got a similar issue. however, buying the incubator, saving the game and then restarting seemed to fix it. again it seems like the object is not initialized (at least that is what i would guess with other languages I have worked with). gdscript is not the best language and the lack of error handling (along with other short comings) really makes proper code design impossible