在运行 Vue.js 应用程序时，我在控制台中收到一条警告，我无法确定它来自哪里（在源代码中），或者至少是从哪个组件中得到它的。
这是控制台输出：
TypeError: Cannot read property 'length' of undefined
at _c.attrs.rules (eval at ./node_modules/vue-loader/lib/template-compiler/index.js?{"id":"data-v-012a975a","hasScoped":true,"optionsId":"0","buble":{"transforms":{}}}!./node_modules/vue-loader/lib/selector.js?type=template&index=0!./src/components/Contact_Form.vue (0.js:300), <anonymous>:252:41)
at VueComponent.validate (vuetify.js?dc48:8564)
at VueComponent.mounted (vuetify.js?dc48:8535)
at callHook (vue.runtime.esm.js?ff9b:2917)
at insert (vue.runtime.esm.js?ff9b:4154)
at Object.invoker [as insert] (vue.runtime.esm.js?ff9b:2019)
at invokeInsertHook (vue.runtime.esm.js?ff9b:5956)
at VueComponent.patch [as __patch__] (vue.runtime.esm.js?ff9b:6175)
at VueComponent.Vue._update (vue.runtime.esm.js?ff9b:2666)
at VueComponent.updateComponent (vue.runtime.esm.js?ff9b:2784)
logError @ vue.runtime.esm.js?ff9b:1737
globalHandleError @ vue.runtime.esm.js?ff9b:1728
handleError @ vue.runtime.esm.js?ff9b:1717
callHook @ vue.runtime.esm.js?ff9b:2919
insert @ vue.runtime.esm.js?ff9b:4154
invoker @ vue.runtime.esm.js?ff9b:2019
invokeInsertHook @ vue.runtime.esm.js?ff9b:5956
patch @ vue.runtime.esm.js?ff9b:6175
Vue._update @ vue.runtime.esm.js?ff9b:2666
updateComponent @ vue.runtime.esm.js?ff9b:2784
get @ vue.runtime.esm.js?ff9b:3138
run @ vue.runtime.esm.js?ff9b:3215
flushSchedulerQueue @ vue.runtime.esm.js?ff9b:2977
(anonymous) @ vue.runtime.esm.js?ff9b:1833
flushCallbacks @ vue.runtime.esm.js?ff9b:1754
Promise.then (async)
microTimerFunc @ vue.runtime.esm.js?ff9b:1802
nextTick @ vue.runtime.esm.js?ff9b:1846
queueWatcher @ vue.runtime.esm.js?ff9b:3064
update @ vue.runtime.esm.js?ff9b:3205
notify @ vue.runtime.esm.js?ff9b:693
reactiveSetter @ vue.runtime.esm.js?ff9b:1010
(anonymous) @ vue-router.esm.js?fe87:2508
(anonymous) @ vue-router.esm.js?fe87:2507
updateRoute @ vue-router.esm.js?fe87:1997
(anonymous) @ vue-router.esm.js?fe87:1875
(anonymous) @ vue-router.esm.js?fe87:1984
step @ vue-router.esm.js?fe87:1714
step @ vue-router.esm.js?fe87:1721
runQueue @ vue-router.esm.js?fe87:1725
(anonymous) @ vue-router.esm.js?fe87:1979
step @ vue-router.esm.js?fe87:1714
(anonymous) @ vue-router.esm.js?fe87:1718
(anonymous) @ vue-router.esm.js?fe87:1964
(anonymous) @ vue-router.esm.js?fe87:1757
(anonymous) @ vue-router.esm.js?fe87:1833
Promise.then (async)
(anonymous) @ vue-router.esm.js?fe87:1780
(anonymous) @ vue-router.esm.js?fe87:1801
(anonymous) @ vue-router.esm.js?fe87:1801
flatMapComponents @ vue-router.esm.js?fe87:1800
(anonymous) @ vue-router.esm.js?fe87:1736
iterator @ vue-router.esm.js?fe87:1943
step @ vue-router.esm.js?fe87:1717
step @ vue-router.esm.js?fe87:1721
runQueue @ vue-router.esm.js?fe87:1725
confirmTransition @ vue-router.esm.js?fe87:1972
transitionTo @ vue-router.esm.js?fe87:1874
init @ vue-router.esm.js?fe87:2494
beforeCreate @ vue-router.esm.js?fe87:540
callHook @ vue.runtime.esm.js?ff9b:2917
Vue._init @ vue.runtime.esm.js?ff9b:4622
Vue @ vue.runtime.esm.js?ff9b:4725
(anonymous) @ main.js?1c90:48
./src/main.js @ app.js:1735
__webpack_require__ @ app.js:708
fn @ app.js:113
0 @ app.js:1813
__webpack_require__ @ app.js:708
(anonymous) @ app.js:806
(anonymous) @ app.js:809