[gnome-dictionary] Add missing signal hanlder in the GdictSourceDialog UI definition

[Emmanuele Bassi <ebassi src gnome org>]

commit 679b3b83f35bc8e602f2d3c8b03736e9156fea33
Author: Emmanuele Bassi <ebassi gnome org>
Date:   Sat Sep 30 16:53:30 2017 +0100

    Add missing signal hanlder in the GdictSourceDialog UI definition
    
    Without it, we won't be able to decide what to do when the user closes
    the dialog.
    
    https://bugzilla.gnome.org/show_bug.cgi?id=762589

 src/gdict-source-dialog.ui |    1 +
 1 files changed, 1 insertions(+), 0 deletions(-)
---
diff --git a/src/gdict-source-dialog.ui b/src/gdict-source-dialog.ui
index 58086bd..e7c83bb 100644
--- a/src/gdict-source-dialog.ui
+++ b/src/gdict-source-dialog.ui
@@ -19,6 +19,7 @@
     <property name="border_width">5</property>
     <property name="resizable">False</property>
     <property name="type_hint">dialog</property>
+    <signal name="response" handler="on_dialog_response" swapped="no"/>
     <child internal-child="vbox">
       <object class="GtkBox" id="source_root">
         <property name="visible">True</property>