Properly stop attacking after player leaves ffa area (like Gurubashi Arena) (#18952)

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

@@ -5874,6 +5874,24 @@ bool Unit::AttackStop()
     return true;
 }
 
+void Unit::ValidateAttackersAndOwnTarget()
+{
+    // iterate attackers
+    UnitVector toRemove;
+    AttackerSet const& attackers = getAttackers();
+    for (Unit* attacker : attackers)
+        if (!attacker->IsValidAttackTarget(this))
+            toRemove.push_back(attacker);
+
+    for (Unit* attacker : toRemove)
+        attacker->AttackStop();
+
+    // remove our own victim
+    if (Unit* victim = GetVictim())
+        if (!IsValidAttackTarget(victim))
+            AttackStop();
+}
+
 void Unit::CombatStop(bool includingCast)
 {
     if (includingCast && IsNonMeleeSpellCast(false))