[OptionsResolver] fix count() and exceptions

| Q             | A
| ------------- | ---
| Bug fix?      | yes
| New feature?  | no
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | -
| License       | MIT
| Doc PR        | -

Please see commits.
Quote from the [documentation of BadMethodCallException](http://php.net/manual/en/class.badmethodcallexception.php):

> Exception thrown if a callback refers to an undefined method or if some arguments are missing.

Neither of these cases applies to the cases where AccessException is thrown.