Why the engine stores non-existent links? And how to clean them?

UATHelper: Packaging (Windows (64-bit)): UE4Editor-Cmd: [2017.07.07-13.25.01:432][ 0]LogUObjectGlobals:warning: Failed to load ‘/Game/Subjects/Energetics/Fukushima/Structures/Reactor/interior/inst_Paint_Red’: Can’t find file '/Game/Subjects/Energetics/Fukushima/Structures/Reactor/interior/inst_Paint_Red’

This object has long been out of the project, but when packing, the log displays warnings.
I apologize for possible mistakes in English

Hey, have you found a solution to that problem ?