Check that there is actually an argument at that position before attempting to do something with it.

stepmania/src/EnumHelper.cpp

@@ -5,6 +5,8 @@
 
 int CheckEnum( lua_State *L, LuaReference &table, int iPos, int iInvalid, const char *szType, bool bAllowInvalid )
 {
+	luaL_checkany( L, iPos );
+
 	if( lua_isnil(L, iPos) )
 	{
 		if( bAllowInvalid )

stepmania/src/LuaBinding.cpp

@@ -226,6 +226,7 @@ bool LuaBinding::CheckLuaObjectType( lua_State *L, int iArg, const char *szType
 #if defined(FAST_LUA)
 	return true;
 #endif
+	luaL_checkany( L, iArg );
 
 	/* Check that szType is in metatable.heirarchy. */
 	if( !luaL_getmetafield(L, iArg, "heirarchy") )

stepmania/src/LuaManager.h

@@ -190,6 +190,7 @@ inline bool MyLua_checkboolean (lua_State *L, int numArg)
  * used to mean "cmd,false". */
 inline bool MyLua_checkintboolean( lua_State *L, int iArg )
 {
+	luaL_checkany( L, iArg );
 	int iType = lua_type( L, iArg );
 	if( iType == LUA_TNUMBER )
 	{