fix: make heap_sort work for empty input (#200)

Author: vil02

src/sorts/heap_sort.jl

@@ -28,6 +28,9 @@ After the largest element has been extracted, the tree is updated to maintain th
   Contributed By:- [Frank Schmitt](https://github.com/frankschmitt)
 """
 function heap_sort!(arr::Vector{T}, gt = >, N::Int = length(arr)) where {T}
+    if isempty(arr)
+        return
+    end 
     n = N
     i = div(n, 2)
     t = -1

test/sorts.jl

@@ -28,6 +28,14 @@ using TheAlgorithms.Sorts
             y = [5, 2, 2, 2, 1, 5, 2, 34, 6, 4, 3, 2, 1, 2, 3, 4, 10, 1]
             f(y)
             @test y == [1, 1, 1, 2, 2, 2, 2, 2, 2, 3, 3, 4, 4, 5, 5, 6, 10, 34]
+
+            z = []
+            f(z)
+            @test z == []
+
+            s = [1]
+            f(s)
+            @test s == [1]
         end
     end
 end