fix: component may be uninitialized on attributeChangedCallback
fix: component may be uninitialized on attributeChangedCallback

this._component._props may throw in attributeChangedCallback.

dispatchEvent is attached to component to pass events to other web-components.

props added via this.attributes may get overwritten by undefined properties in observedAttributes loop.

yysun/apprun,yysun/apprun,yysun/apprun