REALLY NEED HELP WHEN I OPEN A MAP

LogLoad: Error: Old World /Game/ExampleConfigs/cesium_2.cesium_2 not cleaned up by GC! Object World /Game/ExampleConfigs/cesium_2.cesium_2 is being referenced by ScreenCredits_C /Game/ExampleConfigs/cesium_2.cesium_2:ScreenCredits_C_0:
(root) GCObjectReferencer /Engine/Transient.GCObjectReferencer_0