packaging error UE4

Hi there

I am getting this error on attempting packaging…

assertion failed: intexture != nullptr [file:d:/build/++ue4/sync/engine/source/runtime/engine/private/userinterface
/canvasitem.cpp] [line: 382]

Just wondering if anyone can advise on how to narrow down the error?

I am guessing it’s a UI texture problem but I have looked through all my widgets carefully and can’t see anything obviously amiss…

Thanks in advance