chore: address another PR comment

Author: solnic

lib/sentry/test.ex

@@ -862,7 +862,7 @@ defmodule Sentry.Test do
         :ets.delete(collector_table)
       end
 
-      if is_atom(processor_name) do
+      if is_atom(processor_name) and not is_nil(processor_name) do
         Sentry.Test.Registry.drop_processor_routing_for(processor_name)
       end
     end)