Update exception-handling_4.cs (#1356)

Not good to have broken examples  This code generates a CS0168 error because e is not used.  You should definitely use it to set IndexOutOfRangeException to the new exception's InnerException.  You do this correctly in the topic "How to: Handle an Exception Using try/catch (C# Programming Guide)"

Author: rcseacord

docs/csharp/programming-guide/exceptions/codesnippet/CSharp/exception-handling_4.cs

@@ -7,6 +7,6 @@ int GetInt(int[] array, int index)
             catch(System.IndexOutOfRangeException e)
             {
                 throw new System.ArgumentOutOfRangeException(
-                    "Parameter index is out of range.");
+                    "Parameter index is out of range.", e);
             }
-        }
+        }