Adding missing message property on ErrorPrototype

Jint/Native/Error/ErrorPrototype.cs

@@ -18,6 +18,7 @@ namespace Jint.Native.Error
         {
             var obj = new ErrorPrototype(engine, name) { Extensible = true };
             obj.FastAddProperty("constructor", errorConstructor, true, false, true);
+            obj.FastAddProperty("message", "", true, false, true);
 
             if (name != "Error")
             {