Unregistering cell classes causes an assertion failure

[SSheldon]

The UITableView docs for registerClass:forCellReuseIdentifier: say that:

You may specify nil for cellClass if you want to unregister the class from the specified reuse identifier.

However, attempting that with YLTableView causes an assertion failure:

You can only use cells conforming to YLTableViewCell.

The assertion is triggered because, well, nil isn't a YLTableViewCell.

[kfarst]

@SSheldon could you just move the assertion into the if below and accomplish the desired behavior? Seems to pass the tests ^^