优化playing

packages/artplayer/src/player/toggleMix.js

@@ -1,7 +1,7 @@
 export default function toggleMix(art, player) {
     Object.defineProperty(player, 'toggle', {
         value: () => {
-            if (art.isPlaying) {
+            if (player.playing) {
                 player.pause();
             } else {
                 player.play();