I think that sort of code is extremely common. It's a bit less awkward if `current_user` is never nil, but sometimes a non-saved Guest record, letting you write code like this:
@posts = current_user.posts
@posts = @posts.where(user_id: params[:user_id]) if params[:user_id]
Granted, it's pretty awkward code, but I can imagine situations where people might be inclined to write something like that.