Revised to avoid future exceptions.

Author: kenfullscale

Src/StackifyLib.AspNetCore/WebRequestDetailMapper.cs

@@ -166,7 +166,7 @@ internal static void AddKey(string key, string value, Dictionary<string, string>
             {
                 return;
             }
-            dictionary.Add(key,value);
+            dictionary[key] = value;
         }
     }
 }