Dashed line around text box does not appear around RichText field in preview mode

The dashed lines around a RichTextField do not appear when empty, but only for existing documents where a RTE field was added to the template after the document was already created.

Steps to reproduce:

• Create a document type named 'test' with a simple text field
• Create a new document called 'doc1' of type 'test' and add some text.
• Edit the template of type 'test' and add a new RichTextField
• Commit changes
• Browse to the previously created document 'doc1'.

Expected: 'doc1' has an empty RTE with a dashed border
Result: 'doc1' has an empty RTE without a dashed border