500 Internal Server Error

Trying to access array offset on value of type null (8)

#0 /home/xndng68xh3tk/public_html/controllers/work.php(139): flight\Engine->handleError(8, 'Trying to acces...', '/home/xndng68xh...', 139, Array)
#1 /home/xndng68xh3tk/public_html/flight/core/Dispatcher.php(337): {closure}('vistara')
#2 /home/xndng68xh3tk/public_html/flight/core/Dispatcher.php(289): flight\core\Dispatcher::callFunction(Object(Closure), Array)
#3 /home/xndng68xh3tk/public_html/flight/Engine.php(677): flight\core\Dispatcher::execute(Object(Closure), Array)
#4 /home/xndng68xh3tk/public_html/flight/core/Dispatcher.php(395): flight\Engine->_start()
#5 /home/xndng68xh3tk/public_html/flight/core/Dispatcher.php(287): flight\core\Dispatcher::invokeMethod(Array, Array)
#6 /home/xndng68xh3tk/public_html/flight/core/Dispatcher.php(97): flight\core\Dispatcher::execute(Array, Array)
#7 /home/xndng68xh3tk/public_html/flight/Engine.php(183): flight\core\Dispatcher->run('start', Array)
#8 /home/xndng68xh3tk/public_html/flight/core/Dispatcher.php(395): flight\Engine->__call('start', Array)
#9 /home/xndng68xh3tk/public_html/flight/Flight.php(153): flight\core\Dispatcher::invokeMethod(Array, Array)
#10 /home/xndng68xh3tk/public_html/index.php(49): Flight::__callStatic('start', Array)
#11 {main}