[geary: 11/12] Fix crash when opening new IMAP client session as the engine is closing.

[Michael Gratton <mjog src gnome org>]

commit 5b8618a573c861447280cc909e2a72556e37d785
Author: Michael James Gratton <mike vee net>
Date:   Mon Mar 5 23:15:19 2018 +1100

    Fix crash when opening new IMAP client session as the engine is closing.

 .../imap-engine/imap-engine-generic-account.vala   |    2 +-
 .../transport/imap-client-session-manager.vala     |   10 ++++++----
 2 files changed, 7 insertions(+), 5 deletions(-)
---
diff --git a/src/engine/imap-engine/imap-engine-generic-account.vala 
b/src/engine/imap-engine/imap-engine-generic-account.vala
index 7257deb..ece5d80 100644
--- a/src/engine/imap-engine/imap-engine-generic-account.vala
+++ b/src/engine/imap-engine/imap-engine-generic-account.vala
@@ -170,7 +170,7 @@ private abstract class Geary.ImapEngine.GenericAccount : Geary.Account {
         if (!open)
             return;
 
-        // Stop trying to re-use IMAP server connections
+        // Block obtaining and reusing IMAP server connections
         this.remote_ready_lock.reset();
         this.session_pool.discard_returned_sessions = true;
 
diff --git a/src/engine/imap/transport/imap-client-session-manager.vala 
b/src/engine/imap/transport/imap-client-session-manager.vala
index dc00891..e917710 100644
--- a/src/engine/imap/transport/imap-client-session-manager.vala
+++ b/src/engine/imap/transport/imap-client-session-manager.vala
@@ -444,15 +444,18 @@ public class Geary.Imap.ClientSessionManager : BaseObject {
         try {
             yield new_session.connect_async(cancellable);
         } catch (Error err) {
-            debug("[%s] Connect failure: %s", new_session.to_string(), err.message);
-            connection_failed(err);
+            if (!(err is IOError.CANCELLED)) {
+                connection_failed(err);
+            }
             throw err;
         }
 
         try {
             yield new_session.initiate_session_async(this.credentials, cancellable);
         } catch (Error err) {
-            debug("[%s] Initiate session failure: %s", new_session.to_string(), err.message);
+            if (!(err is IOError.CANCELLED)) {
+                connection_failed(err);
+            }
 
             // need to disconnect before throwing error ... don't honor Cancellable here, it's
             // important to disconnect the client before dropping the ref
@@ -463,7 +466,6 @@ public class Geary.Imap.ClientSessionManager : BaseObject {
                     new_session.to_string(), disconnect_err.message);
             }
 
-            connection_failed(err);
             throw err;
         }