Empty page if no course exists

[KrystianKjjk]

Problem not common, because it exists only if db is changed but exists ...
If no course exists, after logIn, app tries to get active course, but db return undefined and that value is saved in localStorage and redux. Later, app tries to read information about it and ... gets an error, page is completely blank, refresh page is useless, because of LS, so to do sth it's necessary clear it.