REST COUNTRIES APP with theme switcher

Hi guys hope you're doing good, i just want to know how you guys manage the way to receive the information of the api when the properties are dynamic, i mean in this case some countries can have "borders countries" or not, so if i do something and a country return an undefined property my app just crash, i manage the way to solve but i dont know if they are good practices, so if you have any recommendations to improve that way, will be very grateful, happy coding.