Ignore operational error when optimize SQLite database on connection

The 'PRAGMA optimize' command can not run on a locked database which may happen
when a nested transaction is started.

Closes #13793

trytond/trytond/backend/sqlite/database.py

@@ -525,7 +525,11 @@ class Database(DatabaseInterface):
         self._conn.execute('PRAGMA foreign_keys = ON')
         self._conn.execute('PRAGMA journal_mode = WAL')
         self._conn.execute('PRAGMA synchronous = NORMAL')
-        self._conn.execute('PRAGMA optimize')
+        try:
+            self._conn.execute('PRAGMA optimize')
+        except DatabaseOperationalError:
+            # database may be locked
+            pass
         return self
 
     def _make_uri(self):