Fix phpstan problems in test db encryption file

www/admin/class_test.db.encryption.php

@@ -136,14 +136,14 @@ if ($res === false) {
 	if (hash_equals($string_hmac, $res['pg_hmac_text'])) {
 		print "libsodium and pgcrypto hash hmac match<br>";
 	}
-}
+	// do compare for PHP and pgcrypto settings
 	$encryptedMessage_template = <<<TEXT
 	-----BEGIN PGP MESSAGE-----
 
 	{BASE64}
 	-----END PGP MESSAGE-----
 	TEXT;
-$base64_string = base64_encode(hex2bin($res['pg_crypt_text']));
+	$base64_string = base64_encode(hex2bin($res['pg_crypt_text']) ?: '');
 	$encryptedMessage = str_replace(
 		'{BASE64}',
 		$base64_string,
@@ -159,9 +159,7 @@ try {
 	} catch (\Exception $e) {
 		print "Error decrypting message: " . $e->getMessage() . "<br>";
 	}
-
-
-// do compare for PHP and pgcrypto settings
+}
 
 print "</body></html>";