Packaged game crashes on load. How to determine the origin for the crash?

I packaged my game and I tried to start it without the editor.
When the game launches it crashes with the following error:

[2022.02.07-18.09.48:704][ 0]Message dialog closed, result: Ok, title: The UE5-FatKnight Game has crashed and will close, text: Assertion failed: BlendSpace != nullptr [File:D:/build/++UE5/Sync/Engine/Source/Runtime/AnimGraphRuntime/Private/AnimNodes/AnimNode_BlendSpaceGraphBase.cpp] [Line: 13]

I took this from the logs, and I can’t see much more helpful information there.
How can I track this?

I’m using UE5 EA.