How to protect SaveLoad script from failing?

Hi, I use a SaveLoad script where I use binary formatter to save an instance of a class. I have a problem when I add a variable to the saved class because, let's say: saved class contains a variable named variable1, then I edit the script and add variable2, then when I launch the game, the game loads save file. It loads variable1 and tries to load variable2 but variable2 is not yet present in save file and it crashes the whole game.

I basically need something like this:

 if (variable2 exists)
 {
 reference the variable
 }

I can't use

 if (variable2)
 {
 reference the variable
 } 

because variable2 is an integer and "can't be converted to boolean". Any ideas?

Here's the code I am using: http://pastebin.com/RjuTMrWw