Fix: Error in creation foreign key

htdocs/install/mysql/migration/2.8.0-2.9.0.sql

@@ -21,6 +21,7 @@ ALTER TABLE llx_bookmark ADD COLUMN position integer        DEFAULT 0;
 -- rename llx_product_det
 ALTER TABLE llx_product_det RENAME TO llx_product_lang;
 ALTER TABLE llx_product_lang ADD UNIQUE INDEX uk_product_lang (fk_product, lang);
+-- V4.1 DELETE FROM llx_product_lang WHERE fk_product NOT IN (SELECT rowid from llx_product);
 ALTER TABLE llx_product_lang ADD CONSTRAINT fk_product_lang_fk_product 	FOREIGN KEY (fk_product) REFERENCES llx_product (rowid);
 
 ALTER TABLE llx_product ADD COLUMN virtual tinyint DEFAULT 0 NOT NULL AFTER tms;