Fixes exception not showing c++ stacktrace in some cases.

PkmnLibSharp/Utilities/NativeException.cs

@@ -11,14 +11,22 @@ namespace PkmnLibSharp.Utilities
             Stack = stack;
         }
 
+        public override string Message 
+        {
+            get
+            {
+                var s = base.Message;
+                if (Stack != null)
+                {
+                    s += Environment.NewLine + Stack;
+                }
+                return s;
+            }
+        }
+
         public override string ToString()
         {
-            var s = base.ToString();
-            if (Stack != null)
-            {
-                s += Environment.NewLine + Stack;
-            }
-            return s;
+            return Message;
         }
     }
 }