Core/Units: Set UNIT_FLAG3_FAKE_DEAD as disallowed flag for database column

Port From (https://github.com/TrinityCore/TrinityCore/commit/a5a2f5af2ddd1ea7166d3e1ee177534fbfbeef3f)

Source/Framework/Constants/CreatureConst.cs

@@ -166,7 +166,7 @@ namespace Framework.Constants
         Disallowed = (Unk0 | /* UnconsciousOnDeath | */ /* AllowMountedCombat | */ GarrisonPet |
                                                                    /* UiCanGetPosition | */ /* AiObstacle | */ AlternativeDefaultLanguage | /* SuppressAllNpcFeedback | */
                                                                    IgnoreCombat | SuppressNpcFeedback | Unk10 | Unk11 |
-                                                                   Unk12 | /* FakeDead | */ /* NoFacingOnInteractAndFastFacingChase | */ /* UntargetableFromUi | */
+                                                                   Unk12 | FakeDead | /* NoFacingOnInteractAndFastFacingChase | */ /* UntargetableFromUi | */
                                                                    /* NoFacingOnInteractWhileFakeDead | */ AlreadySkinned | /* SuppressAllNpcSounds | */ /* SuppressNpcSounds | */
                                                                    AllowInteractionWhileInCombat | Unk21 | /* DontFadeOut | */ Unk23 |
                                                                    ForceHideNameplate | Unk25 | Unk26 | Unk27 |

Source/Game/Entities/Player/Player.cs

@@ -5473,7 +5473,7 @@ namespace Game.Entities
 
             // not unfriendly/hostile
             if (!creature.IsInteractionAllowedWhileHostile() && creature.GetReactionTo(this) <= ReputationRank.Unfriendly)
-                return nullptr;
+                return null;
 
             if (creature.IsInCombat() && !creature.IsInteractionAllowedInCombat())
                 return null;