As @wergeld said, you need to pass 0-based values to options, otherwise you won't get displayed nothing at all. For nulls it's no possible, since this doesn't have value.
Now,you need to set minPointLength
, to some value (like 10), then even 0-values will be displayed as small bars. See demo: http://jsfiddle.net/EJK4e/12/
Just to be on the same page - to display tooltip, you need point graphic, otherwise there will be no hover event for triggering tooltip to show up.