Timetable bug: given invalid period, the program doesn't do anything

[GERARDJM018]

The image above is when I try to use invalid period (high to low). The command used: 'edit i:1 c/mon: 8-10, 10-12 tue: 11-13 thu: 13-11'. The invalid input should be 13-11 as it doesn't make sense for a period to be decreasing (travel back to past). However, the program doesn't show error message when I try using the command.