Avoid the exception during Dispose by only calling SetObject() when there is a HttpContext (#1219)

Author: xecrets

src/React.Web/TinyIoCAspNetExtensions.cs

@@ -63,9 +63,10 @@ public void ReleaseObject()
 			var item = GetObject() as IDisposable;
 
 			if (item != null)
+			{
 				item.Dispose();
-
-			SetObject(null);
+				SetObject(null);
+			}
 		}
 
 		/// <summary>