Core/Vehicles:

- Grab correct npc entry from npc_spellclick_spells in case of player vehicle. Fixes DB errors added in my previous changeset
- Allow aura's with SPELL_AURA_CONTROL_VEHICLE to stack if there are enough free seats, even if spellIds are identical.
- Fix a possible infinite loop. Thanks to manuel for spotting

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

@@ -6594,7 +6594,7 @@ void AuraEffect::HandleAuraSetVehicle(AuraApplication const * aurApp, uint8 mode
 
     if (apply)
     {
-        if (!target->CreateVehicleKit(vehicleId))
+        if (!target->CreateVehicleKit(vehicleId, 0))
             return;
     }
     else if (target->GetVehicleKit())

src/server/game/Spells/SpellMgr.cpp

@@ -3177,6 +3177,34 @@ bool SpellMgr::CanAurasStack(Aura const *aura1, Aura const *aura2, bool sameCast
         }
     }
 
+    bool isVehicleAura1 = false;
+    bool isVehicleAura2 = false;
+    uint8 i = 0;
+    while (i < MAX_SPELL_EFFECTS && !(isVehicleAura1 && isVehicleAura2))
+    {
+        if (spellInfo_1->EffectApplyAuraName[i] == SPELL_AURA_CONTROL_VEHICLE)
+            isVehicleAura1 = true;
+        if (spellInfo_2->EffectApplyAuraName[i] == SPELL_AURA_CONTROL_VEHICLE)
+            isVehicleAura2 = true;
+
+        ++i;
+    }
+
+    if (isVehicleAura1 && isVehicleAura2)
+    {
+        Vehicle* veh = NULL;
+        if (aura1->GetOwner()->ToUnit())
+            veh = aura1->GetOwner()->ToUnit()->GetVehicleKit();
+
+        if (!veh)           // We should probably just let it stack. Vehicle system will prevent undefined behaviour later
+            return true;
+
+        if (!veh->GetAvailableSeatCount())
+            return false;   // No empty seat available
+
+        return true;        // Empty seat available (skip rest)
+    }
+
     uint32 spellId_1 = GetLastSpellInChain(spellInfo_1->Id);
     uint32 spellId_2 = GetLastSpellInChain(spellInfo_2->Id);