Do not assume JSON block when mapping array

If the following code snippet is the first line of a program, JSHint
incorrectly assumes it is JSON when doing array destructuring checks:

```
['foo', 'bar', 'baz'].forEach(function(name) {
  console.log(name);
});
```

Fixes #1446
Merge pull request #1688 from artnez/fix-incorrect-json-detection

Do not assume JSON block when mapping array