修复内容高度较高时连线消失

src/components/Tree.vue

@@ -141,8 +141,8 @@ export default {
       this.ctx = document.getElementById('line-drawer').getContext('2d');
     },
     drawLine(height) {
+      this.fitHeight = height > HEIGHT ? height : HEIGHT;
       setTimeout(() => {
-        this.fitHeight = height > HEIGHT ? height : HEIGHT;
         this.ctx.clearRect(0, 0, WIDTH, height > HEIGHT ? height : HEIGHT);
         this.ctx.lineWidth = 1;
         this.ctx.strokeStyle = '#bbbbbb';