Update v1.2.5c

Version 1.2.5c is a small hotfix update to address a few technical issues.

• Fixed memory leak caused by certain combinations of item and groove modifiers stacking on units.
  
• Conquest: Fixed various issues caused by units loaded into transport units. Units are now unloaded automatically when progressing to the next event.
  
• Fixed crash rendering preview image for custom maps in map selection screen.
  
• Editor: Fixed crash when trying to edit properties of treasure chest.