Core/Entities: Fixed an issue where creatures would not properly assist formation members in certain scenarios. Tagging #21967.

(cherry picked from commit a001bc63b1182babddbb188f7c762c6168a98b5c)

src/server/game/Combat/ThreatManager.cpp

@@ -19,6 +19,7 @@
 #include "Creature.h"
 #include "CombatPackets.h"
 #include "CreatureAI.h"
+#include "CreatureGroups.h"
 #include "MotionMaster.h"
 #include "ObjectAccessor.h"
 #include "Player.h"
@@ -391,6 +392,8 @@ void ThreatManager::AddThreat(Unit* target, float amount, SpellInfo const* spell
         SaveCreatureHomePositionIfNeed(cOwner);
         if (CreatureAI* ownerAI = cOwner->AI())
             ownerAI->JustEngagedWith(target);
+        if (CreatureGroup* formation = cOwner->GetFormation())
+            formation->MemberEngagingTarget(cOwner, target);
     }
 }
 

src/server/game/Entities/Unit/Unit.cpp

@@ -35,7 +35,6 @@
 #include "CreatureAI.h"
 #include "CreatureAIImpl.h"
 #include "CreatureAIFactory.h"
-#include "CreatureGroups.h"
 #include "DB2Stores.h"
 #include "Formulas.h"
 #include "GameTime.h"
@@ -7682,10 +7681,6 @@ void Unit::EngageWithTarget(Unit* enemy)
         m_threatManager.AddThreat(enemy, 0.0f, nullptr, true, true);
     else
         SetInCombatWith(enemy);
-
-    if (Creature* creature = ToCreature())
-        if (CreatureGroup* formation = creature->GetFormation())
-            formation->MemberEngagingTarget(creature, enemy);
 }
 
 void Unit::AttackedTarget(Unit* target, bool canInitialAggro)