Update event.js

Author: neSpecc

src/models/event.js

@@ -80,7 +80,13 @@ class Event {
           this.payload[prop] = schema[prop];
         }
       } else {
-        this[prop] = schema[prop];
+        if (prop === 'payload' && this.payload !== undefined) {
+          schema[prop].forEach(item => {
+            this.payload[item.key] = item.value;
+          });
+        } else {
+          this[prop] = schema[prop];
+        }
       }
     });
   }