Switch to using Dictionary initializer, and add check for SupportsHeaders

Crawl/Crawl/Crawl.cs

@@ -117,18 +117,23 @@ namespace Microsoft.DecisionService.Crawl
                 catch (WebException we)
                 {
                     HttpWebResponse httpResponse = we.Response as HttpWebResponse;
-                    if (we.Status == WebExceptionStatus.ServerProtocolViolation)
+                    if (we.Status == WebExceptionStatus.ServerProtocolViolation && we.Response != null)
                     {
                         // Get a little more telemetry about what is going on here.
-                        IDictionary<string, string> traceData = new Dictionary<string, string>();
-                        traceData["Response.SupportsHeaders"] = we.Response.SupportsHeaders.ToString();
+                        IDictionary<string, string> traceData = new Dictionary<string, string>()
+                        {
+                            { "Response.SupportsHeaders", we.Response.SupportsHeaders.ToString() }
+                        };
 
+                        if (we.Response.SupportsHeaders)
+                        {
                             for (int i = 0; i < we.Response.Headers.Count; i++)
                             {
                                 string headerName = we.Response.Headers.GetKey(i);
                                 string headerValue = we.Response.Headers.Get(i);
                                 traceData[$"Response.Headers.{headerName}"] = headerValue;
                             }
+                        }
 
                         if (httpResponse != null)
                         {