imapc: Fix local state if mailbox is empty after reconnection If local indexes had more than 0 mails, but after reconnection the remote IMAP server replied with "* 0 EXISTS", the mails in local index weren't expunged. This could have resulted in: Panic: file imapc-sync.c: line 328 (imapc_initial_sync_check): assertion failed: (mail_index_is_expunged(view, lseq) || seq_range_exists(&ctx->mbox->delayed_expunged_uids, luid))