Datatable "tab"-navigation

When dynamic data loading is enabled, if you navigate using the “tab”, under certain conditions, we get an error.

https://snippet.webix.com/j8jb8d4z

increase loadahead, say, to 500
or
try this

  on:{
    onBeforeEditStart: function(cell){
      if(!cell.row)return false;								
    }
  }