[geary] Avoid detaching a detached composer

[Robert Schroll <rschroll src gnome org>]

commit 28a489cf22bb48e46dfd14e53446cbbd28d54840
Author: Robert Schroll <rschroll gmail com>
Date:   Fri Jan 23 23:16:13 2015 -0500

    Avoid detaching a detached composer
    
    https://bugzilla.gnome.org/show_bug.cgi?id=743433

 src/client/composer/composer-widget.vala |    2 ++
 1 files changed, 2 insertions(+), 0 deletions(-)
---
diff --git a/src/client/composer/composer-widget.vala b/src/client/composer/composer-widget.vala
index af529f3..f14f911 100644
--- a/src/client/composer/composer-widget.vala
+++ b/src/client/composer/composer-widget.vala
@@ -1048,6 +1048,8 @@ public class ComposerWidget : Gtk.EventBox {
     }
     
     private void on_detach() {
+        if (state == ComposerState.DETACHED)
+            return;
         Gtk.Widget? focus = container.remove_composer();
         ComposerWindow window = new ComposerWindow(this);
         if (focus != null) {