Fix: Clean before adding foreign key

htdocs/install/mysql/migration/3.6.0-3.7.0.sql

@@ -96,10 +96,11 @@ ALTER TABLE llx_product ADD CONSTRAINT fk_product_barcode_type FOREIGN KEY (fk_b
 -- Added missing relations of llx_product_price
 -- fk_user_author
 ALTER TABLE  llx_product_price ADD INDEX idx_product_price_fk_user_author (fk_user_author);
-update llx_product_price set fk_user_author = null where fk_user_author = 0;
+UPDATE llx_product_price set fk_user_author = null where fk_user_author = 0;
 ALTER TABLE  llx_product_price ADD CONSTRAINT fk_product_price_user_author FOREIGN KEY (fk_user_author) REFERENCES  llx_user (rowid);
 -- fk_user_author
 ALTER TABLE  llx_product_price ADD INDEX idx_product_price_fk_product (fk_product);
+DELETE from llx_product_price where fk_product NOT IN (SELECT rowid from llx_product);
 ALTER TABLE  llx_product_price ADD CONSTRAINT fk_product_price_product FOREIGN KEY (fk_product) REFERENCES  llx_product (rowid);
 
 ALTER TABLE llx_commande_fournisseur ADD COLUMN fk_account integer AFTER date_livraison;