Rigs-of-rods: MP issues with previously loaded terrains

[CuriousMike56]

This happened during a MP session on Debug_Server_MitCity, causing all players to crash. I had to investigate.

• Launch two RoR clients. (For one of the clients, I copied the install directory and created a config folder in it to prevent any conflicts with my Documents folder)
• On one client, click Single player and load Auriga Proving Grounds.
• On the other client, join a server with a fixed terrain set (e.g. Debug_Server_MitCity or Debug_Server_Neo):
  
  I will be calling the left window Client A and the right window Client B.
• Press ESC and click Return to menu on Client A, then join the same server Client B is on.
• All pre-spawned loads from the previous terrain Client A was on will attempt to spawn, causing Client A to get kicked for spawning too many actors:
  
  
  The first couple of times I tried reproducing this crash, Client B crashed with a UTF-8 error:
  
  Loading a terrain without any pre-spawned vehicles (e.g. Simple Test Terrain) won't immediately cause a crash when joining, but if Client B has a vehicle spawned, then Client A will crash:
  
  Here's another example, I loaded RaceMax on Client A and joined Debug_Server_Neo on Client B, then on Client A I returned to menu and joined the server:
  

[tritonas00]

Indeed
(it would be nice if instead of random characters on imgui error dialog we had "Auto-kicked for having too many vehicles")

[ulteq]

it would be nice if instead of random characters on imgui error dialog we had "Auto-kicked for having too many vehicles"

We should open a separate issue for that bug.