Countries Website with React

I've managed to do the challenge but still having some problems with the React code, first one being that some countries pages cannot be entered because the country doesen't have one of the elements that is being shown (for example any island country can't be showed because it doesen't have any border countries and therefore it's giving out some error and displays an empty page), second problem is I haven't figured out how to link the border countries to get to that specific country on click and the last problem is when you're on a country specific page and refresh it gives back a blank page haven't figured out how to fix that.

If anyone has any feedback or is able to help on these issues I would be more than thankful.