Fix required field 'sale_email'

plugin/buycourses/database.php

@@ -337,6 +337,7 @@ $globalTable->addColumn('seller_address', \Doctrine\DBAL\Types\Type::STRING);
 $globalTable->addColumn('seller_email', \Doctrine\DBAL\Types\Type::STRING);
 $globalTable->addColumn('next_number_invoice', \Doctrine\DBAL\Types\Type::INTEGER);
 $globalTable->addColumn('invoice_series', \Doctrine\DBAL\Types\Type::STRING);
+$globalTable->addColumn('sale_email', \Doctrine\DBAL\Types\Type::STRING);
 $globalTable->setPrimaryKey(['id']);
 
 $invoiceTable = $pluginSchema->createTable(BuyCoursesPlugin::TABLE_INVOICE);

plugin/buycourses/src/buy_course_plugin.class.php

@@ -188,7 +188,8 @@ class BuyCoursesPlugin extends Plugin
                 seller_address varchar(255) NOT NULL,
                 seller_email varchar(255) NOT NULL,
                 next_number_invoice int unsigned NOT NULL,
-                invoice_series varchar(255) NOT NULL
+                invoice_series varchar(255) NOT NULL,
+                sale_email varchar(255) NOT NULL
             )";
             $res = Database::query($sql);
             if (!$res) {