Fatal error: Uncaught TypeError: array_keys(): Argument #1 ($array) must be of type array, null given in /disk_1/www/cz/ostwest/www/content/pl/page/references.php:30
Stack trace:
#0 /disk_1/www/cz/ostwest/www/content/pl/page/references.php(30): array_keys(NULL)
#1 /disk_1/www/cz/ostwest/www/content/pl/index.php(16): include('/disk_1/www/cz/...')
#2 /disk_1/www/cz/ostwest/www/index.php(22): include('/disk_1/www/cz/...')
#3 {main}
  thrown in /disk_1/www/cz/ostwest/www/content/pl/page/references.php on line 30