Fix custom column creation

src/calibre/library/custom_columns.py

@@ -467,7 +467,8 @@ class CustomColumns(object):
                           books_ratings_link as bl,
                           ratings as r
                      WHERE {lt}.value={table}.id and bl.book={lt}.book and
-                           r.id = bl.rating and r.rating <> 0) avg_rating
+                           r.id = bl.rating and r.rating <> 0) avg_rating,
+                     value AS sort
                 FROM {table};
 
                 CREATE VIEW tag_browser_filtered_{table} AS SELECT
@@ -481,7 +482,8 @@ class CustomColumns(object):
                           ratings as r
                      WHERE {lt}.value={table}.id AND bl.book={lt}.book AND
                            r.id = bl.rating AND r.rating <> 0 AND
-                           books_list_filter(bl.book)) avg_rating
+                           books_list_filter(bl.book)) avg_rating,
+                     value AS sort
                 FROM {table};
 
                 '''.format(lt=lt, table=table),