Not really a bug, DOM parsers will ignore that space and selectors will all work correctly. QA locators should not have an issue with it when they parse the HTML correctly.
The space is there because it is a separator between classes and we have 2 classes on that element, the second class is a user class and default not set and inserts an empty string. Will see if I can cleanup the code a bit so that it doesn't generate that space when no user class is set.