Hi,
thank you for your report. It seems like it is a problem in PolyLang rather than in my plugin. The errors that you showed clearly say that PolyLang produces this bug (as you may see the paths - they point to PolyLang, not to Foodlist). I never used this plugin, and all I can say is that I can guarantee Foodlist to be compatible with WPML (and if it's not, I can fix it fast), but I have zero knowledge of PolyLang. Have you tried contacting its developers? If they need me to add something special to the plugin, so that PolyLang would be functional, they can reach me by email: art <at> artprima.cz.
Regards