fix: slide在执行play时候可能为null导致报错 (#830)

Co-authored-by: xxyCoder <1696944145@qq.com>

Author: xxyCoder

src/components/slide/slide.vue

@@ -252,7 +252,7 @@
       _play() {
         clearTimeout(this._timer)
         this._timer = setTimeout(() => {
-          this.slide.next()
+          this.slide && this.slide.next()
         }, this.interval)
       },
       _deactivated() {