fix(core): add null guards for vehicle pointers in render setup

[CanerKaraca23]

Problem

1. When ModelInfoMgr::SetupRender(CVehicle *ptr) was called with a null pointer (e.g. during certain world rendering passes or detached object/component setups), dereferencing ptr->SetupRender() caused an immediate access violation crash:

   Unhandled exception at 0x06B41E06 in modelextras.asi (+0x71e06): 0xC0000005: Access violation reading location 0x00000024.
   

2. In LicensePlate::CCustomCarPlateMgr_SetupMaterialPlatebackTexture, calling m_VehData.Get(pCurrentVeh) when pCurrentVeh was not yet initialized or null resulted in null pointer dereference crashes.

Solution

1. Added early null guard in ModelInfoMgr::SetupRender: if (!ptr) { return; }.
2. Added null guard in LicensePlate::CCustomCarPlateMgr_SetupMaterialPlatebackTexture: if (!pCurrentVeh) { return material; }.