[Loot] Remove unnecessary loot error messages.

[Kinglykrab]

• These messages are only sent when you loot a corpse that is mid-decay (i.e. no items and you go to loot it immediately) or if you try to loot a non-corpse entity.
• The ent != 0 shows up a lot if you're trying to loot too quickly and really isn't an error, the server just hasn't caught up to decay the corpse before you try to loot.
• Add LootItem_Struct to give more verbosity to Handle_OP_LootItem.