Throw better exception when response has no body and the user want to read it.

Author: honfika

src/Titanium.Web.Proxy/Http/Response.cs

@@ -1,5 +1,6 @@
 using System;
 using System.ComponentModel;
+using Titanium.Web.Proxy.Exceptions;
 using Titanium.Web.Proxy.Extensions;
 using Titanium.Web.Proxy.Models;
 
@@ -118,6 +119,11 @@ internal override void EnsureBodyAvailable(bool throwWhenNotReadYet = true)
                 return;
             }
 
+            if (!HasBody)
+            {
+                throw new BodyNotFoundException("Response don't have a body.");
+            }
+
             if (!IsBodyRead && throwWhenNotReadYet)
             {
                 throw new Exception("Response body is not read yet. " +