[PATCH]: Fix places where we expect non-null loops in the loop array

[Daniel Berlin]

>> you change the loop numbers when you swap them or not).
>
> We can do more than just swap loops.
> We can more or less arbitrarily change the loop nesting order.
> To prevent problems caused by trying to figure out where a given loop went, 
> and because the transformations involve more than just loop swapping, we 
> never actually mess with the cfg.
> We just rewrite the loop conditions, induction variables, and bodies so that 
> they act as if they were swapped.
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
s/swapped/reversed, skewed, interchanged, or scaled with respect to 
some other loop/