Image not found error when opening Datetime or Datetime range element

Description

Steps to reproduce:

1. Create a form with a Datetime or Datetime range element, and a Submit element.
2. Add the form to a page, and then publish the page.
3. View the form.
4. Click on the date picker.

Expected:

The date picker is displayed.

Actual:

The date picker is displayed but there is an 404 error in the console.