You can use the special monitoring POUs provided in TwinCAT to enable the implicit error monitoring (e.g. fixing an array index out of boundary issue automatically) in your program.

Right click your POUs folder, select add, then POU FOR implicit checks.. 

Select the functions you'd want to add into your program. You will need do a full recompile and download your program after adding these functions. 

More information about these implicit check POUs can be found here.