To me it looks like evar21 on your setup holds the internal search keyword. Where do you get the value for evar21 from? is it when the customer types it into the search box and you do a server call to set evar21 (or set evar21 before you do the s.t() call) ie record the internal search term on the page where it's typed or most likely on the results page (since this is much simpler).
If it's on the search results page then you need a couple of things to make your internal search work correctly
1) previous page name in a prop and/or evar this way you can breakdown the internal search term by previous page to find out where the customer typed in the term rather than looking at the current page which is your search results page
2) you need an event for a successful internal search and an event for a failed internal search. That way you can get away from instances etc and your successful internal search and failed internal search term will only fire when there is an internal search so that 24M instances/occurrences etc of 'none' will go away. It also allows you to gauge your entire internal search usage when you use the internal search event applied against your other conversion variables (in campaign xxxx how many internal searches happened, where did they happen and what was searched for....
adding more to your internal search results (number of results, success/fail, suggested terms, breadcrumbs, was a result clicked?, which one? was it a suggested term? etc. You can build a pretty good internal search tracking practice with a few choice settings you record for internal search.