Update merge_sort_fastest.py

I have modified the code a little to make it work as expected!

sorts/merge_sort_fastest.py

@@ -7,14 +7,15 @@ Worst Case Scenario : O(n)
 def merge_sort(LIST):
     start = []
     end = []
-    a = LIST[0]
-    b = LIST[-1]
-    while (LIST.index(a) == LIST.index(b) and len(LIST) <=2):
+    while LIST:
         a = min(LIST)
         b = max(LIST)
         start.append(a)
         end.append(b)
-        LIST.remove(a)
-        LIST.remove(b)
+        try:
+            LIST.remove(a)
+            LIST.remove(b)
+        except ValueError:
+            continue
     end.reverse()
-return start + end
+    return (start + end)