Assertion failed: (Index >= 0) & (Index < ArrayNum) [File:D:\build\++UE5\Sync\Engine\Source\Runtime\Core\Public\Containers\Array.h] [Line: 771] Array index out of bounds: 0 from an array of size 0

[meTheBEE]

Corrupted DDC is a common cause.
makefile
Delete all contents in that folder.
C:\Users<YourUsername>\AppData\Local\UnrealEngine\Common\DerivedDataCache
Navigate to your project’s folder.
Delete these folders:
/Saved/
/Intermediate/
/DerivedDataCache/ (if present)

It solved my issue.

Then try launching Unreal Engine again.
CopyEdit

C:\Users\<YourUsername>\AppData\Local\UnrealEngine\Common\DerivedDataCache\