This error occurred while I was baking. What happened

Development Modding ARK: Survival Evolved
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Ensure condition failed: bValidRootIndex [File:H:\SVN_Ark\Engine\Source\Runtime\Engine\Private\Animation\AnimBlueprintGeneratedClass.cpp] [Line: 219]

Unhandled Exception: EXCEPTION_ACCESS_VIOLATION reading address 0x00000060

VERSION: 0.0
UE4Editor-Engine.dll!UnknownFunction (0x000007fedd5426c7) + 0 bytes [UnknownFile:0]
UE4Editor-Engine.dll!UnknownFunction (0x000007fedd59ad11) + 0 bytes [UnknownFile:0]
UE4Editor-Engine.dll!UnknownFunction (0x000007fedd604670) + 0 bytes [UnknownFile:0]
UE4Editor-CoreUObject.dll!UnknownFunction (0x000007fedf5d9ebe) + 0 bytes [UnknownFile:0]
UE4Editor-CoreUObject.dll!UnknownFunction (0x000007fedf647db6) + 0 bytes [UnknownFile:0]
UE4Editor-CoreUObject.dll!UnknownFunction (0x000007fedf654bbd) + 0 bytes [UnknownFile:0]
UE4Editor-UnrealEd.dll!UnknownFunction (0x000007fedadc1584) + 0 bytes [UnknownFile:0]
UE4Editor-UnrealEd.dll!UnknownFunction (0x000007fedadfd2f7) + 0 bytes [UnknownFile:0]
UE4Editor.exe!UnknownFunction (0x000000013f2365be) + 0 bytes [UnknownFile:0]
UE4Editor.exe!UnknownFunction (0x000000013f22f92c) + 0 bytes [UnknownFile:0]
UE4Editor.exe!UnknownFunction (0x000000013f22fa8a) + 0 bytes [UnknownFile:0]
UE4Editor.exe!UnknownFunction (0x000000013f23be10) + 0 bytes [UnknownFile:0]
UE4Editor.exe!UnknownFunction (0x000000013f23cd49) + 0 bytes [UnknownFile:0]
kernel32.dll!UnknownFunction (0x00000000777359cd) + 0 bytes [UnknownFile:0]
ntdll.dll!UnknownFunction (0x000000007789383d) + 0 bytes [UnknownFile:0]
ntdll.dll!UnknownFunction (0x000000007789383d) + 0 bytes [UnknownFile:0]