Add a metadata_last_modified attribute to the Metadata object returned by get_metadata

src/calibre/gui2/tag_view.py

@@ -574,8 +574,10 @@ def __init__(self, data=None, category_icon=None, icon_map=None,
 
     def break_cycles(self):
         for x in self.children:
-            if hasattr(x, 'break_cycles'):
+            try:
                 x.break_cycles()
+            except:
+                pass
         self.parent = self.icon_state_map = self.bold_font = self.tag = \
                 self.icon = self.children = None
 

src/calibre/library/database2.py

@@ -833,6 +833,7 @@ def get_metadata(self, idx, index_is_id=False, get_cover=False):
         mi.pubdate     = row[fm['pubdate']]
         mi.uuid        = row[fm['uuid']]
         mi.title_sort  = row[fm['sort']]
+        mi.metadata_last_modified = row[fm['last_modified']]
         formats = row[fm['formats']]
         if not formats:
             formats = None