mpchristmas2017 is a "DLC pack" released by Rockstar Games. The dlc.rpf is an encrypted archive file that contains all the assets for this DLC, such as vehicle models, weapon skins, clothing items, and festive props.
If your game crashes to desktop (CTD) without an error code, or throws a ERR_GEN_INVALID error, the issue usually stems from one of three scenarios: Update X64 Dlcpacks Mpchristmas2017 Dlc.rpf