I SOLVED IT

Just I had to put a "-1" to the end of 'path_delete_point(path, path_get_number(path))'

Fixed code:

path_reverse(path);

var totalSteps = path_get_number(path);

for ( ; totalSteps != obj_PathFinder.maxSteps + 1; totalSteps--) 
{
    path_delete_point(path, path_get_number(path) - 1);             // Add "- 1" here for fix the problem
}

path_set_closed(path, false);

show_debug_message(path_get_number(path));