Alpha 4 patch 6 hotfix 3

[h3]Added/changed:[/h3]

• Another bunch of small optimizations
  
• Added a message if no export stock on wagon arrival
  
• Messengers from river towns will not visit in winter now
  

[h3]Fixed:[/h3]

• Trading boats had water in them if post-processing turned off
  
• Crash after relocating animals
  
• It was possible to build smeltery with entrance on water
  
• Crash when hovering smeltery (in rare cases)
  
• Could create a house with blocked entrance leading to white lines
  
• Foresters stopped chopping trees in some of the previous versions
  
• A few more cases of false "inaccessible"
  
• A few more cases of white lines