I need to use `If` but with only one option that is if "a" then do "b", else do nothing. So I wrote `If[a,b]` but the problem is that if it is not `a` it returns `Null` in my output.
How to avoid this?

Here is the specific example I was working on.

I am looking for the number of comparisons performed by the quick sort algorithm. Here is the code from [Rosetta code](http://rosettacode.org/wiki/Sorting_algorithms/Quicksort) with my additions

 QuickSort[x_List] := 
 Module[{pivot, aa = 0, bb = 0}, If[Length@x <= 1, Return[x]];
 pivot = First[x];
 aa = If [Length[Cases[x, j_ /; j < pivot]] > 1, 
 Length[Cases[x, j_ /; j < pivot]] - 1 , Sequence[]];
 bb = If [Length[Cases[x, j_ /; j < pivot]] > 1, 
 Length[Cases[x, j_ /; j > pivot]] - 1 , Sequence[]]; 
 count = count + aa + bb;
 Flatten@{QuickSort[Cases[x, j_ /; j < pivot]], 
 Cases[x, j_ /; j == pivot], 
 QuickSort[Cases[x, j_ /; j > pivot]]} ; Return[count] ]

now if you run `QuickSort[{4, 3, 2, 1, 5}]` you will get `2+2 Null` instead of 4