[CssSelector] fixed numeric attribute issue
bug #9970 [CssSelector] fixed numeric attribute issue (jfsimon)

This PR was merged into the 2.3 branch.

Discussion
----------

[CssSelector] fixed numeric attribute issue

This PR adds a cast from number to string when parsing a numeric attribute value.

| Q             | A
| ------------- | ---
| Bug fix?      | yes
| New feature?  | no
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | #9968

Commits
-------

613535a [CssSelector] fixed numeric attribute issue