Webform when used within Form Builder is missing proper element IDs

When editing Webform with the Form Builder module, there is a minor issue in that the "id" attribute in the HTML is always missing from the element wrapper. Instead of id="webform-component-element-name", it's always just id="webform-component-". While this stems from the approach used in the Form Builder Webform UI, the problem is much easier to fix on the Webform side and makes the existing theme function more robust for additional scenarios besides displaying the form for end-users to fill out.