Ensure resident model resources get added to the manifest, fixes error models from missing resources in manifest. This would specifically happen if a server starts a game / map a second time, the resources would remain resident, so when a client does their initial join these models are missing from the manifest resulting in an error. If the client had previously joined on the first time their resources would already be resident and not error. Simplest way to do it, rather then change (and slow down) how the rest of the resource system works. If a resource we try to preload returns an error handle, don't keep the handle alive. Map resources specifically will become valid and load automatically after this.