Getting an error during initialization.

RimWorld 0.17.1557 rev1153
Verse.Log:Message(String)
RimWorld.VersionControl:LogVersionNumber()
Verse.Root:CheckGlobalInit()
Verse.Root:Start()
Verse.Root_Entry:Start()

Found no usable data when trying to get defs from file SubCategories.xml
Verse.Log:Error(String)
Verse.<AllDefsFromAsset>c__Iterator226:MoveNext()
Verse.ModContentPack:LoadDefs(IEnumerable`1)
Verse.LoadedModManager:LoadAllActiveMods()
Verse.PlayDataLoader:DoPlayLoad()
Verse.PlayDataLoader:LoadAllPlayData(Boolean)
Verse.Root:<Start>m__84E()
Verse.LongEventHandler:RunEventFromAnotherThread(Action)
Verse.LongEventHandler:<UpdateCurrentAsynchronousEvent>m__84C()

This is with only the Core files and LED Lights loading, took a while to hunt down exactly which mod was causing this... No error from loading all the other mods I use.