a page without spreadsheet still loads spreadsheet related javascript

Steps to Reproduce

1. create and run a page with https://github.com/keikai/dev-ref like

<zk>
<button/>
</zk>

2. open developer tool / Source tab

Current Result

zss.wpd and zssex.wpd are still loaded

Expected Result

no zss.wpd and zssex.wpd loaded

Debug Info

if keikai follows zk spec, it should only load zss.wpd when there is <spreadsheet> on a zul.