I don’t think now supports < or >. You have to use the isAfter methods as demonstrated in Design Pattern: Time Of Day.
But your error is happening before that line.
I still think that it isn’t worked before because if a trick of timing and it is failing here because one of the Astro items had not yet been populated by the astro binding.
Check to see if this test items are NULL and log out of they are.
You can mitigate this by using restoreOnStartup on these Items or by triggering the role that checks on when either of those items receive an update.