core (memory/sqlite): return 0 instead of None when user has no file yet

sat/memory/sqlite.py

@@ -993,7 +993,7 @@ class SqliteStorage(object):
             query,
             (owner.userhost(), self.profiles[client.profile])
         )
-        return ret[0][0]
+        return ret[0][0] or 0
 
     def _fileUpdate(self, cursor, file_id, column, update_cb):
         query = 'SELECT {column} FROM files where id=?'.format(column=column)