我的代码中有错误。错误如下：v.context.$implicit未定义
问题是，有时它会出错，有时它不会......有人能解释一下为什么会发生这种情况吗？
这是我的html代码：

<ng-container *ngFor="let time of item.timeInfo | keys" >
    <ion-row *ngIf="time == thisDay"> 
      <ion-col col-3 no-padding>
        <ng-container *ngIf="checkTime(); else closeButton">
          <button small ion-button block color="secondary" outline> OPEN </button>
        </ng-container>
        <ng-template #closeButton>
          <button small ion-button block color="danger" outline>Close </button>
        </ng-template>
      </ion-col>
      <ion-col col-9 >
        {{ item.timeInfo[thisDay].open }} - {{ item.timeInfo[thisDay].close }}
      </ion-col>
    </ion-row>
  </ng-container>

下面是我的json代码：

"item":{
   "timeInfo": {
            "Sat": {
                "open": "11:00",
                "close": "21:00"
            },
            "Sun": {
                "open": "9:00",
                "close": "21:30"
            },
            "Mon": {
                "open": "11:00",
                "close": "22:30"
            },
            "Tue": {
                "open": "12:00",
                "close": "22:00"
            },
            "Web": {
                "open": "12:00",
                "close": "22:30"
            },
            "Thu": {
                "open": "9:30",
                "close": "22:30"
            },
            "Fri": {
                "open": "12:30",
                "close": "22:00"
            }
        },
 };

这是我的版本：

@ionic/cli-utils  : 1.15.2
ionic (Ionic CLI) : 3.15.2

local packages:
@ionic/app-scripts : 3.0.0
Ionic Framework    : ionic-angular 3.7.1

System:
Node : v6.11.2
npm  : 5.4.2
OS   : Windows 8.1

Misc:
backend : pro

有人能帮我吗？？Tyvm