Fix some ie bug

packages/artplayer/src/player/playMix.js

@@ -13,7 +13,7 @@ export default function playMix(art, player) {
         value() {
             const promise = $video.play();
 
-            if (promise.then) {
+            if (promise && promise.then) {
                 promise.then().catch((err) => {
                     notice.show = err;
                     throw err;

packages/artplayer/src/subtitle.js

@@ -111,6 +111,7 @@ export default class Subtitle extends Component {
         return fetch(url)
             .then((response) => response.arrayBuffer())
             .then((buffer) => {
+                if (!window.TextDecoder) return;
                 const decoder = new TextDecoder(opt.encoding || subtitle.encoding);
                 const text = decoder.decode(buffer);