I have this issue when i run the setup:upgrade command, can anybody explain to me what is this error and how to fix it:
DOMDocument::loadXML(): Argument #1 ($source) must not be empty#0 /var/www/html/rakuten_magento/vendor/magento/framework/Config/Dom.php(451): DOMDocument->loadXML() #1 /var/www/html/rakuten_magento/vendor/magento/framework/Config/Dom.php(148): Magento\Framework\Config\Dom->_initDom() #2 /var/www/html/rakuten_magento/vendor/magento/framework/Config/Reader/Filesystem.php(153): Magento\Framework\Config\Dom->merge() #3 /var/www/html/rakuten_magento/vendor/magento/framework/Config/Reader/Filesystem.php(132): Magento\Framework\Config\Reader\Filesystem->_readFiles() #4 /var/www/html/rakuten_magento/vendor/magento/framework/Setup/Declaration/Schema/Declaration/ReaderComposite.php(46): Magento\Framework\Config\Reader\Filesystem->read() #5 /var/www/html/rakuten_magento/vendor/magento/framework/Setup/Declaration/Schema/SchemaConfig.php(76): Magento\Framework\Setup\Declaration\Schema\Declaration\ReaderComposite->read() #6 /var/www/html/rakuten_magento/setup/src/Magento/Setup/Model/DeclarationInstaller.php(57): Magento\Framework\Setup\Declaration\Schema\SchemaConfig->getDeclarationConfig() #7 /var/www/html/rakuten_magento/setup/src/Magento/Setup/Model/Installer.php(846): Magento\Setup\Model\DeclarationInstaller->installSchema() #8 /var/www/html/rakuten_magento/setup/src/Magento/Setup/Model/Installer.php(894): Magento\Setup\Model\Installer->declarativeInstallSchema() #9 /var/www/html/rakuten_magento/setup/src/Magento/Setup/Console/Command/UpgradeCommand.php(146): Magento\Setup\Model\Installer->installSchema() #10 /var/www/html/rakuten_magento/vendor/symfony/console/Command/Command.php(255): Magento\Setup\Console\Command\UpgradeCommand->execute() #11 /var/www/html/rakuten_magento/vendor/symfony/console/Application.php(1009): Symfony\Component\Console\Command\Command->run() #12 /var/www/html/rakuten_magento/vendor/symfony/console/Application.php(273): Symfony\Component\Console\Application->doRunCommand() #13 /var/www/html/rakuten_magento/vendor/magento/framework/Console/Cli.php(115): Symfony\Component\Console\Application->doRun() #14 /var/www/html/rakuten_magento/vendor/symfony/console/Application.php(149): Magento\Framework\Console\Cli->doRun() #15 /var/www/html/rakuten_magento/bin/magento(23): Symfony\Component\Console\Application->run() #16 {main}
You may have some empty xml file Or the xml may not be valid.
Following is the function triggering the error.
protected function _initDom($xml) { $dom = new \DOMDocument(); $useErrors = libxml_use_internal_errors(true); $res = $dom->loadXML($xml); // Line 451
Where can i find this function ?