[geary/wip/730682-refine-convo-list: 8/11] Fix a critical when switching between folders and previews still loading.

[Michael Gratton <mjog src gnome org>]

commit 48a9d3c50d139ca827122f38754c458403c173ef
Author: Michael James Gratton <mike vee net>
Date:   Fri Jan 5 10:54:48 2018 +1100

    Fix a critical when switching between folders and previews still loading.

 src/client/conversation-list/preview-loader.vala |    6 +++++-
 1 files changed, 5 insertions(+), 1 deletions(-)
---
diff --git a/src/client/conversation-list/preview-loader.vala 
b/src/client/conversation-list/preview-loader.vala
index 65f6354..b840582 100644
--- a/src/client/conversation-list/preview-loader.vala
+++ b/src/client/conversation-list/preview-loader.vala
@@ -1,6 +1,6 @@
 /*
- * Copyright 2017 Michael Gratton <mike vee net>
  * Copyright 2016 Software Freedom Conservancy Inc.
+ * Copyright 2017-2018 Michael Gratton <mike vee net>
  *
  * This software is licensed under the GNU Lesser General Public License
  * (version 2.1 or later).  See the COPYING file in this distribution.
@@ -58,6 +58,10 @@ public class PreviewLoader : Geary.BaseObject {
         );
     }
 
+    ~PreviewLoader() {
+        this.load_timer.reset();
+    }
+
     public void load_remote() {
         this.loading_local_only = false;
         this.do_load.begin();