Vehicle variant for add-on vehicles is ignored until applied twice #5333

Describe the bug

Spawning an add-on vehicle (model requested with engineRequestModel) and setting any variants doesn't work as it does on vanilla vehicles. However, applying variants again with setVehicleVariant makes it work.

https://streamable.com/avxj3t

The vehicle from the video can be downloaded here. The variants used are 0, 255.

Steps to reproduce

1. Spawn any add-on vehicle created with engineRequestModel.
2. Call createVehicle with any two variants that the vehicle model has. In the video I use 0, 255.
3. Observe that variant variables are synchronized but the grille (variant 0 model) doesn't render until variants are applied again with setVehicleVariant.

Version

MTA:SA Server v1.7-untested-26841

Additional context

No response

Relevant log output

Security Policy

• I have read and understood the Security Policy and this issue is not security related.