ApiQueryBase::titleToKey and ApiQueryBase::keyToTitle;

ApiQueryBase::titleToKey and ApiQueryBase::keyToTitle;
Don't bother constructing a title object when the $title/$key is ''. (Why were we doing this check after creating the title object, there's no point in even creating a big object if we're just going to check the old string we already had to see if it's empty)
And as a bonus, use trim() so that user input such as ' ' does not dish out an error (There really isn't much difference between "&title=" and "&title= " if one shouldn't output an error, why should the other?).