For UE 5.3, the error “SpawnActor failed because no class was specified” dont just make an error in the log.
It make the engine crash.
Unhandled Exception: EXCEPTION_ACCESS_VIOLATION reading address 0x0000000000000208
UnrealEditor_Engine!UWorld::SpawnActor() [D:\build\++UE5\Sync\Engine\Source\Runtime\Engine\Private\LevelActor.cpp:448]
UnrealEditor_Engine!UWorld::SpawnActor() [D:\build\++UE5\Sync\Engine\Source\Runtime\Engine\Private\LevelActor.cpp:438]
UnrealEditor_SimpleShooter!AShooterCharacter::AShooterCharacter() [H:\Program Files\Unreal Projects\SimpleShooter\Source\SimpleShooter\ShooterCharacter.cpp:14]
UnrealEditor_CoreUObject!UClass::CreateDefaultObject() [D:\build\++UE5\Sync\Engine\Source\Runtime\CoreUObject\Private\UObject\Class.cpp:4390]
UnrealEditor_CoreUObject!UClass::InternalCreateDefaultObjectWrapper() [D:\build\++UE5\Sync\Engine\Source\Runtime\CoreUObject\Private\UObject\Class.cpp:4987]
UnrealEditor_CoreUObject!UObjectLoadAllCompiledInDefaultProperties() [D:\build\++UE5\Sync\Engine\Source\Runtime\CoreUObject\Private\UObject\UObjectBase.cpp:825]
EDIT : Once again, I am a complete idiot.
Writing the code too quickly, I did not realise that I wrote the SpawnActor method in the constructor instead of the BeginPlay .