Fixed a pointer-difference, comparison-with-zero expression.

Fixed a pointer-difference, comparison-with-zero expression.

Some GCC C compilers can't subtract higher pointers from lower pointers properly, when those pointers must be scaled (because they point to objects that are wider than a char). The scaling is done as unsigned which makes the difference positive instead of negative.

So, a broken expression was changed into a direct comparison between the two pointers.