fix message deletion on server

before a message is actually deleted,
we verify that server_folder+server_uid matches the Message-ID,
so that we do not delete the wrong message by accident.
the reason for that is that, to my knowledge, server_folder+server_uid
are not necessarily stable but Message-ID is.

anyway, this check was broken and set the server_uid to 0 in all cases -
where it should be set to 0 _only_ on mismatches.

src/imap/mod.rs

@@ -957,8 +957,8 @@ impl Imap {
                                 remote_message_id,
                                 message_id,
                             );
+                            *uid = 0;
                         }
-                        *uid = 0;
                     }
                     Err(err) => {
                         warn!(