Core/Creature: Reset loot recipient group on respawn.

Fixes issue 4051.

--HG--
branch : trunk

src/server/game/Entities/Creature/Creature.cpp

@@ -967,6 +967,7 @@ void Creature::SetLootRecipient(Unit *unit)
     if (!unit)
     {
         m_lootRecipient = 0;
+        m_lootRecipientGroup = 0;
         RemoveFlag(UNIT_DYNAMIC_FLAGS, UNIT_DYNFLAG_LOOTABLE|UNIT_DYNFLAG_TAPPED);
         return;
     }