custom-tab-bar: 调整因差异导致切换tab箭头状态不正确的问题

pages/template/custom-tab-bar/custom-tab-bar.uvue

@@ -80,10 +80,11 @@
     },
     methods: {
       onTabClick(index : number) {
-        this.setSelectedIndex(index);
-        if (index == 0) {
+        if (this.selectedIndex == index && index == 0) {
+          this.displayArrow = false;
           (this.$refs["tab1"]! as ComponentPublicInstance).$callMethod('scrollTop', 0)
         }
+        this.setSelectedIndex(index);
       },
       onTabPageEvent(top : number) {
         this.displayArrow = top > this.tabViewHeight