Assert absence does not work properly on selectors containing '?'

I have added the following assertion:

```
assert_nothing_raised { assert_select "a[href='http://example.org?query=value']", false }
```

It raises exception:

```
Expected at least 1 element matching "a[href='http://example.orgfalsequery=value']", found 0..
Expected 0 to be >= 1.
```

As you can see the problem is that `?` is substituted by `false`, and assertion checks for presence, not absence.
