Support for optional object properties

Let's say we have the following Fact:
```
{
"firstName": "John",
"lastName" : "doe",
"age" : 26,
"address" : {
"streetAddress": "naist street",
"city" : "Nara",
"postalCode" : "630-0192"
},
"phoneNumbers": [
{
"type" : "iPhone",
"number": "0123-4567-8888"
},
{
"type" : "home",
"number": "0123-4567-8910"
}
]
}
```
The following rule snippet should return true in my understanding:

```
{
fact: 'a',
path: `$..phoneNumbers..title`,
operator: 'doesNotContain',
value: 'SOMETITLE'
},
```

However this will evaluate to false, as "title" is not present in the object.
The actual use case I have is that the dynamic fact ist an array of objects which can be an empty array sometimes (due to input params for the fact).

Supporting this use case would be very valuable, otherwise additional custom operators are necessary.

沒有指定檔案、測試或進入點。使用缺少的標題和空物件陣列重現所提供的事實和規則，然後追蹤 JSON 路徑和 doesNotContain 評估；當所要求的選用屬性案例在不需要自訂運算子的情況下傳回預期結果時，即表示完成。

由索引模型根據 Issue 內容生成。