minor bug fix of 'null' and 'undefined'

src/views/user/Dashboard.vue

@@ -42,7 +42,7 @@ function getUserInfo() {
 function updateInfo() {
   userInfoUpdate({
     name: newName.value,
-    password: null,
+    password: undefined,
     address: address.value,
   }).then(res => {
     if (res.data.code === '000') {
@@ -64,9 +64,9 @@ function updateInfo() {
 
 function updatePassword() {
   userInfoUpdate({
-    name: null,
+    name: undefined,
     password: password.value,
-    address: null
+    address: undefined
   }).then(res => {
     if (res.data.code === '000') {
       password.value = ''