fix: 关联上级，上级账号可以为空

src/views/relationAdmin/index.vue

@@ -35,6 +35,9 @@ export default {
         const managerId = ref('');
         const relationUsername = ref('');
         const onSubmit = async () => {
+            if (!relationUsername.value) {
+                relationUsername.value = '';
+            }
             // 提交表单
             const { data } = await setRelationAdmin(username.value, managerId.value, relationUsername.value);