Fall back to title field first before using string rep for meta title.

mezzanine/core/models.py

@@ -146,7 +146,7 @@ def meta_title(self):
         Accessor for the optional ``_meta_title`` field, which returns
         the string version of the instance if not provided.
         """
-        return self._meta_title or str(self)
+        return self._meta_title or getattr(self, "title", str(self))
 
     def description_from_content(self):
         """