refactor: fix TypeError in BaseUtils

1) CodeIgniter\Database\Live\DbUtilsTest::testUtilsCSVFromResult
TypeError: str_replace(): Argument #3 ($subject) must be of type array|string, int given

/home/runner/work/CodeIgniter4/CodeIgniter4/system/Database/BaseUtils.php:217
/home/runner/work/CodeIgniter4/CodeIgniter4/tests/system/Database/Live/DbUtilsTest.php:186

2) CodeIgniter\Database\Live\DbUtilsTest::testUtilsXMLFromResult
TypeError: xml_convert(): Argument #1 ($str) must be of type string, int given, called in /home/runner/work/CodeIgniter4/CodeIgniter4/system/Database/BaseUtils.php on line 249

/home/runner/work/CodeIgniter4/CodeIgniter4/system/Helpers/xml_helper.php:20
/home/runner/work/CodeIgniter4/CodeIgniter4/system/Database/BaseUtils.php:249
/home/runner/work/CodeIgniter4/CodeIgniter4/tests/system/Database/Live/DbUtilsTest.php:199

Author: kenjis

system/Database/BaseUtils.php

@@ -212,7 +212,7 @@ public function getCSVFromResult(ResultInterface $query, string $delim = ',', st
             $line = [];
 
             foreach ($row as $item) {
-                $line[] = $enclosure . str_replace($enclosure, $enclosure . $enclosure, $item ?? '') . $enclosure;
+                $line[] = $enclosure . str_replace($enclosure, $enclosure . $enclosure, (string) $item) . $enclosure;
             }
 
             $out .= implode($delim, $line) . $newline;
@@ -244,7 +244,7 @@ public function getXMLFromResult(ResultInterface $query, array $params = []): st
             $xml .= $tab . '<' . $element . '>' . $newline;
 
             foreach ($row as $key => $val) {
-                $val = (! empty($val)) ? xml_convert($val) : '';
+                $val = (! empty($val)) ? xml_convert((string) $val) : '';
 
                 $xml .= $tab . $tab . '<' . $key . '>' . $val . '</' . $key . '>' . $newline;
             }