Initialize static variable

Signed-off-by: Deukhoofd <Deukhoofd@gmail.com>

CInterface/Core.cpp

@@ -1,6 +1,7 @@
 #include "Core.hpp"
 
 std::string ExceptionHandler::_creatureLibLastException = "";
+std::string ExceptionHandler::_creatureLibLastExceptionStacktrace = "";
 
 export const char* CreatureLib_C_GetLastException() { return ExceptionHandler::GetLastException(); }
 export const char* CreatureLib_C_GetLastExceptionStacktrace() { return ExceptionHandler::GetLastExceptionStacktrace(); }