Index: lib/sup/maildir.rb
===================================================================
--- lib/sup/maildir.rb	(revision 503)
+++ lib/sup/maildir.rb	(working copy)
@@ -99,12 +99,12 @@
 
   def start_offset
     scan_mailbox
-    @ids.first
+    @ids.first || 0
   end
 
   def end_offset
     scan_mailbox
-    @ids.last
+    @ids.last || 0
   end
 
   def pct_done; 100.0 * (@ids.index(cur_offset) || 0).to_f / (@ids.length - 1).to_f; end