update function example to catch exception

examples/functions/index.js

@@ -9,5 +9,9 @@ lua.registerFunction('add', function(a, b){
 lua.doStringSync("print('Result in Lua: ' .. add(10, 5))");
 
 var lua_two = new nodelua.LuaState('two');
-// this will throw an error
-lua_two.doStringSync("add(10, 5)");
+try{
+    lua_two.doStringSync("add(10, 5)");
+} catch(e){
+    console.log("Error: ");
+    console.log(e);
+}