DoN's 3D-Pathfinding / Flying-AI system (with full source!)

Do anyone have what’s wrong here? My project keeps crashing with this error:


Unhandled Exception: EXCEPTION_ACCESS_VIOLATION reading address 0xffffffff


UE4Editor_DonAINavigation_0001!ADonNavigationManager::SchedulePathfindingTask() [C:\Users\diego\Documents\Unreal Projects\DemoProject\Plugins\DonAINavigation-master\Source\DonAINavigation\Private\DonNavigationManager.cpp:2137]
UE4Editor_DonAINavigation_0001!ADonNavigationManager::execSchedulePathfindingTask() [C:\Users\diego\Documents\Unreal Projects\DemoProject\Plugins\DonAINavigation-master\Intermediate\Build\Win64\UE4Editor\Inc\DonAINavigation\DonNavigationManager.gen.cpp:1741]