fix：回复chartBox的校验 以及 this.editChart.param.statistics为空事的默认值

nezha-fronted/src/components/page/dashboard/chartBox.vue

@@ -1036,6 +1036,8 @@ export default {
       this.confirmAdd()
     },
     confirmAdd () {
+      this.$refs.chartForm.validate((valid) => {
+        if (valid) {
           this.prevent_opt.save = true
           this.elementTarget = [] // 初始化清空参数
           if (this.editChart.type !== 'url' && this.editChart.type != 'text') {
@@ -1127,6 +1129,8 @@ export default {
               })
             }
           }
+        }
+      })
     },
     // 获取metric列表
     getSuggestMetric () {
@@ -1755,6 +1759,9 @@ export default {
         } else {
           this.createData(this.showPanel.id, '', n.unit)
         }
+        if ( this.editChart.param && !this.editChart.param.statistics) {
+          this.editChart.param.statistics = 'null'
+        }
       }
     }
   },