refactor: Apply rector changes

Signed-off-by: GitHub <noreply@github.com>

Author: nextcloud-command

lib/Controller/PageController.php

@@ -270,7 +270,7 @@ protected function provideTemplate(string $template, ?Form $form = null, array $
 	 */
 	protected function insertHeaderOnIos(): void {
 		$USER_AGENT_IPHONE_SAFARI = '/^Mozilla\/5\.0 \(iPhone[^)]+\) AppleWebKit\/[0-9.]+ \(KHTML, like Gecko\) Version\/[0-9.]+ Mobile\/[0-9.A-Z]+ Safari\/[0-9.A-Z]+$/';
-		if (preg_match($USER_AGENT_IPHONE_SAFARI, $this->request->getHeader('User-Agent'))) {
+		if (preg_match($USER_AGENT_IPHONE_SAFARI, (string) $this->request->getHeader('User-Agent'))) {
 			Util::addHeader('meta', [
 				'name' => 'viewport',
 				'content' => 'width=device-width, initial-scale=1, minimum-scale=1, maximum-scale=1'