Edit in office doesn't work in Firefox, if WebDAV Launcher configuration not being complete. Improve this to include a useful error for the user.

When using a newer version of Firefox, if you have installed the webdav connector add-on for Firefox and click on the link edit on office at the attachment screen, nothing happens. Additionally, if the WebDAV Launcher add-on is not installed, you are not prompted to install it.

Steps to Reproduce

1. Open a vanilla Firefox
2. Go to a Confluence page with an Office Document
3. Click Edit in Office (or go to Tools - Attachments and try to edit in office from there)
   • You should be prompted to install the WebDAV connector at this point, according to this document, but you are not.
4. Install the add-on manually
5. Try to edit the document again
   • Still, nothing happens, as thought the button or link has no action attached.

Workaround

This behaviour occurs because the WebDAV Launcher has not been configured. You will need to install the connector manually, then configure it following this document. You will then be able to Edit in Office through Firefox.

Hopes and Dreams

The behaviour of the WebDAV connector could be improved, to show an error or warning if the add on has not been configured. Our documentation indicates that the user will be taken to the download location if the add-on is not installed, so this should also occur.