When creating an element to make into a dropdown you can add the attribute 'required'. Instead of this it would be better if the external wrapper was made required so the browser has an element it can focus on, rather than erroring when the page is submitted and validated by the browser.
You can wrap your dropdown inside a container (such as a div) and initialize the validator explicitly on that container, if applicable. See this demo for reference: http://demos.telerik.com/kendo-ui/validator/index