update player.d.ts

packages/artplayer/src/player/stateMix.js

@@ -3,7 +3,7 @@ import { def } from '../utils';
 export default function stateMix(art) {
     const states = ['mini', 'pip', 'fullscreen', 'fullscreenWeb'];
     def(art, 'state', {
-        get: () => states.find((name) => art[name]) || '',
+        get: () => states.find((name) => art[name]) || 'standard',
         set(name) {
             for (let index = 0; index < states.length; index++) {
                 const prop = states[index];