[geary] Fix critical warning closing engine when search table update is running.

[Michael Gratton <mjog src gnome org>]

commit 0262d32e8782d6842cc67cf4e4a2332d0f8a160f
Author: Michael James Gratton <mike vee net>
Date:   Tue Aug 2 22:41:52 2016 +1000

    Fix critical warning closing engine when search table update is running.
    
    * src/engine/imap-db/imap-db-account.vala
      (Account::populate_search_table_batch_async): Ensure the DB is open
      before proceeding with the query.

 src/engine/imap-db/imap-db-account.vala |    1 +
 1 files changed, 1 insertions(+), 0 deletions(-)
---
diff --git a/src/engine/imap-db/imap-db-account.vala b/src/engine/imap-db/imap-db-account.vala
index 3078648..e686fcc 100644
--- a/src/engine/imap-db/imap-db-account.vala
+++ b/src/engine/imap-db/imap-db-account.vala
@@ -1616,6 +1616,7 @@ private class Geary.ImapDB.Account : BaseObject {
     
     private async bool populate_search_table_batch_async(int limit, Cancellable? cancellable)
         throws Error {
+        check_open();
         debug("%s: Searching for up to %d missing indexed messages...", account_information.id,
             limit);