CiviMail, TinyMCE - selecting a template does not replace html_message content

Using trunk
To reproduce, create a civimail template, select TinyMCE as the wysiwyg editor. Then create a mailing, and try to choose the template.

Expected result: template content replaces html body
Actual result: html body not replaced

patch attached- have to use tinymce api to access the editor content.