Core/Units: added a helper to check if a limited target aura exists without creating an empty element in the container

src/server/scripts/Spells/spell_mage.cpp

@@ -982,7 +982,7 @@ class spell_mage_nether_vortex : public AuraScript
 
     bool CheckProc(ProcEventInfo& /*eventInfo*/)
     {
-        return GetTarget()->GetLimitedCastAuras(SPELL_MAGE_SLOW).empty();
+        return GetTarget()->HasLimitedTargetAuraForSpell(SPELL_MAGE_SLOW);
     }
 
     void HandleEffectProc(AuraEffect const* aurEff, ProcEventInfo& eventInfo)