Fix #1238636 [Calibre 1.6 / Find Duplicates Plugin /ERROR: Unhandled exception: <b>ValueError</b>:tuple.index(x): x not in tuple](https://bugs.launchpad.net/calibre/+bug/1238636)

src/calibre/gui2/library/alternate_views.py

@@ -827,6 +827,9 @@ class GridView(QListView):
         changed = old_marked | current_marked
         m = self.model()
         for book_id in changed:
+            try:
                 self.update(m.index(m.db.data.id_to_index(book_id), 0))
+            except ValueError:
+                pass
 
 # }}}