Update v1.2.5c

Version 1.2.5c is a small hotfix update to address a few technical issues. [list] [*] 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. [/list]