sclass attribute doesn't work as designed

Steps to Reproduce

1. run <spreadsheet height="100%" sclass="myclass"/>
2. check spreadsheet's root DOM element

Current Result

<div id="kCxP0" style="height:100%;" class="zssheet">...</div>
myclass is not rendered on the root DOM

Expected Result

<div id="kCxP0" style="height:100%;" class="zssheet myclass">...</div>