Not working - merge_sort method to "merge" 2-element sorted items

merge_sort method
 1) while loop, while the last element in array isn't nil
 2) (need to delete this) if an element is nil, skip
 3) if num1 > num2, add num2 to merged array
    if num2 > num1, add num1 to merged array
 4) in the non-merged array, the num added changed to nil
 5) because the value is now nil, the index for num added to merged
    array is incremented by 1
 6) if both num1 and num2 are nil, increment the indexes by 1