Fix richtext widget inside toggleable layout widget

Steps to reproduce:

• in a layout, use a richtext_with_mimetype widget (like the one used by the Note document type)
• place this layout inside a toggleable layout widget that uses ajax saving
• toggle the widget from text/html to markdown

=> when saving the form, nothing happens.

When adding an a4j:log tag to the rendering, it appears that problem is linked to the js hook to trigger saving of the tinyMCE editor:

warn [10:09:01.076]: richfaces.queue: ajax submit error: tinyMCE.editors['nxl_JenkinsReportSummary_tabLayout:nxw_sub1_toggledForm:nxl_JenkinsDutyComments_edit:nxw_richtext_with_mimetype_1_editor'] is undefined