Clear trait events

src/trait_manager/view/TraitView.js

@@ -47,6 +47,7 @@ export default Backbone.View.extend({
     model.view = this;
     this.listenTo(model, 'change:label', this.render);
     this.listenTo(model, 'change:placeholder', this.rerender);
+    this.events = {};
     eventCapture.forEach(event => (this.events[event] = 'onChange'));
     this.delegateEvents();
     this.init();