FIX Correct page title shown when restoring a page, instead of html of t...

...ree node. That is a fix for the regression mentioned in https://github.com/silverstripe/silverstripe-framework/pull/1996

Reproduction step:
- Delete a draft
- Restore the draft, observe the success message is "Restored <some HTML/> successfully", as opposed to "Restored 'My page' successfully". 

This patch addresses this issue