fix(Core/Unit): Prevent creature evade when on another unit's threat list (#25328)

Co-authored-by: blinkysc <blinkysc@users.noreply.github.com>
Co-authored-by: Rocco Silipo <108557877+Rorschach91@users.noreply.github.com>

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

@@ -11493,12 +11493,12 @@ Unit* Creature::SelectVictim()
         return target;
     }
 
-    // last case when creature must not go to evade mode:
-    // it in combat but attacker not make any damage and not enter to aggro radius to have record in threat list
-    // Note: creature does not have targeted movement generator but has attacker in this case
-    for (AttackerSet::const_iterator itr = m_attackers.begin(); itr != m_attackers.end(); ++itr)
-        if ((*itr) && CanCreatureAttack(*itr) && !(*itr)->IsPlayer() && !(*itr)->ToCreature()->HasUnitTypeMask(UNIT_MASK_CONTROLLABLE_GUARDIAN))
-            return nullptr;
+    // Don't evade if another unit has us on their threat list — evading would
+    // end the bidirectional combat reference and remove us from their threat list,
+    // causing them to lose their target (e.g. an NPC fighting a guardian whose
+    // CanAIAttack rejects the NPC).
+    if (!m_threatManager.GetThreatenedByMeList().empty())
+        return nullptr;
 
     if (GetVehicle())
         return nullptr;