Core/Spells: fixed a crash in periodic health leech aura effects when the caster is no longer present

src/server/game/Spells/Auras/SpellAuraEffects.cpp

@@ -5919,7 +5919,8 @@ void AuraEffect::HandlePeriodicHealthLeechAuraTick(Unit* target, Unit* caster) c
         GetCasterGUID().ToString().c_str(), target->GetGUID().ToString().c_str(), damage, GetId(), absorb);
 
     // SendSpellNonMeleeDamageLog expects non-absorbed/non-resisted damage
-    caster->SendSpellNonMeleeDamageLog(target, GetId(), damage, GetSpellInfo()->GetSchoolMask(), absorb, resist, false, 0, crit);
+    if (caster)
+        caster->SendSpellNonMeleeDamageLog(target, GetId(), damage, GetSpellInfo()->GetSchoolMask(), absorb, resist, false, 0, crit);
     damage = damageInfo.GetDamage();
 
     // Set trigger flag