[framework] fixed seoRobotsTxtContent null value in settings (#2732)

src/Migrations/Version20230404071649.php

@@ -24,7 +24,7 @@ public function up(Schema $schema): void
 
             if ($seoRobotsTxtContentSettingCount <= 0) {
                 $this->sql(
-                    'INSERT INTO setting_values (name, domain_id, value, type) VALUES (\'seoRobotsTxtContent\', :domainId, \'\', \'string\')',
+                    'INSERT INTO setting_values (name, domain_id, value, type) VALUES (\'seoRobotsTxtContent\', :domainId, NULL, \'string\')',
                     ['domainId' => $domainId],
                 );
             }

src/Migrations/Version20230817135234.php

@@ -0,0 +1,26 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Shopsys\FrameworkBundle\Migrations;
+
+use Doctrine\DBAL\Schema\Schema;
+use Shopsys\MigrationBundle\Component\Doctrine\Migrations\AbstractMigration;
+
+class Version20230817135234 extends AbstractMigration
+{
+    /**
+     * @param \Doctrine\DBAL\Schema\Schema $schema
+     */
+    public function up(Schema $schema): void
+    {
+        $this->sql('UPDATE setting_values SET value = \'\' WHERE name = \'seoRobotsTxtContent\' AND value IS NULL');
+    }
+
+    /**
+     * @param \Doctrine\DBAL\Schema\Schema $schema
+     */
+    public function down(Schema $schema): void
+    {
+    }
+}