[imp] Error Deleting Message in IMP 2.3.7-cvs

[Rodney Barnett]

This morning I installed the latest IMP and horde from CVS and found a test case
for this problem.

1. Turn off the trash folder option.
2. Turn off the "return to the mailbox listing after deleting a message" option.
3. Create a new folder.
4. Copy four messages into the folder.
5. Open the folder.
6. Delete the first message in the folder.  (Do NOT purge.)
7. Turn on the trash folder option.
8. Open the folder again.
9. Open the second message.
10. Delete the open message from the message view.  That should leave you
viewing message 1 of 2 though the message view will say 2 of 3.
11. Delete the open message from the message view.

If you're like me, you'll now see a page like the following:

----------------------
Warning: Undefined offset: 1 in /var/www/html/horde/imp/message.php on line 253

Warning: Cannot add header information - headers already sent by (output started
at /var/www/html/horde/imp/message.php:253) in
/var/www/html/horde/imp/message.php on line 364
----------------------

Rodney