Fixed bug when the parser stopped working met statement unnamed.

The CSS:
```css
b { color: red; }
{ color: green; }
a {color: blue; }
```
earlier parsed to
```js
{
    "type": "stylesheet",
    "stylesheet": {
        "rules": [
            {
                "type": "rule",
                "selectors": [
                    "b"
                ],
                "declarations": [
                    {
                        "type": "declaration",
                        "property": "color",
                        "value": "red"
                    }
                ]
            }
        ]
    }
}
```

now
```js
{
    "type": "stylesheet",
    "stylesheet": {
        "rules": [
            {
                "type": "rule",
                "selectors": [
                    "b"
                ],
                "declarations": [
                    {
                        "type": "declaration",
                        "property": "color",
                        "value": "red"
                    }
                ]
            },
            {
                "type": "rule",
                "selectors": [],
                "declarations": [
                    {
                        "type": "declaration",
                        "property": "color",
                        "value": "green"
                    }
                ]
            },
            {
                "type": "rule",
                "selectors": [
                    "a"
                ],
                "declarations": [
                    {
                        "type": "declaration",
                        "property": "color",
                        "value": "blue"
                    }
                ]
            }
        ]
    }
}
```