url_redirector errors in log

[Aki]

I don't think I have url_redirector module enabled. Should I ignore this error from logs?

task; lua_metric_symbol_callback: call to (SETTINGS_CHECK) failed (2): /usr/share/rspamd/lua/url_redirector.lua:260: attempt to index local 'url' (a nil value); trace: [1]:{/usr/share/rspamd/lua/url_redirector.lua:260 - <unknown> [Lua]};

[Aki]

I've found this was caused by something I did elsewhere, adding a symbol in a prefilter. In /etc/rspamd/rspamd.local.lua I added this:

rspamd_config.MYPRE = {
 type = 'prefilter',
  priority = 10,
  callback = function(task)
   task:insert_result('GRPA', 0)
  end
}

I want to explain and ask about that in another thread, but on a general note, why did that cause problem for the url_redirector module?