Don't throw on not-matching elements in visitPseudoClassSelector

[TheCarpetMerchant]

This is for #223. I personally do not wish to have an exception thrown because of a simple typo in an html selector, that seems wildly excessive. The selector wouldn't be able to be used anyway. While silently ignoring errors is not great, in this case it is the better option for me in practice. This PR is here moreso to raise awareness on the issue then anything else ; ideas on how to handle this by giving more leverage over the matching process to devs are welcome.