[gnome-documents] application: Avoid CRITICALs if a primary instance is already present

[Debarshi Ray <debarshir src gnome org>]

commit 9964208e298769a11748f30468d352a6cbb44183
Author: Debarshi Ray <debarshir gnome org>
Date:   Thu Jun 8 16:10:57 2017 +0200

    application: Avoid CRITICALs if a primary instance is already present
    
    The dbus_unregister method can be invoked more than once. Trying to
    unexport an already unexported GDBusInterfaceSkeleton led to:
      GLib-GIO-CRITICAL **:
        g_dbus_interface_skeleton_unexport_from_connection: assertion
        'interface_->priv->connections != NULL' failed
    
    https://bugzilla.gnome.org/show_bug.cgi?id=783548

 src/application.js |    5 ++++-
 1 files changed, 4 insertions(+), 1 deletions(-)
---
diff --git a/src/application.js b/src/application.js
index 4e55bf8..77495de 100644
--- a/src/application.js
+++ b/src/application.js
@@ -453,7 +453,10 @@ const Application = new Lang.Class({
     },
 
     vfunc_dbus_unregister: function(connection, path) {
-        this._searchProvider.unexport(connection);
+        if (this._searchProvider != null) {
+            this._searchProvider.unexport(connection);
+            this._searchProvider = null;
+        }
 
         this.parent(connection, path);
     },