[epiphany] Fix About dialog surviving the initial close

[Michael Catanzaro <mcatanzaro src gnome org>]

commit 65053f3d8fa7723109f61d31b195a70b0e1d0dbe
Author: Michael Catanzaro <mcatanzaro igalia com>
Date:   Thu Oct 18 22:57:38 2018 -0500

    Fix About dialog surviving the initial close
    
    This regressed in the previous commit. Last minute change. Whoops!

 src/window-commands.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)
---
diff --git a/src/window-commands.c b/src/window-commands.c
index e37948903..58e896582 100644
--- a/src/window-commands.c
+++ b/src/window-commands.c
@@ -623,6 +623,7 @@ window_cmd_show_about (GSimpleAction *action,
   gtk_about_dialog_add_credit_section (dialog, _("Contributors"), (const char **)contributors);
 
   gtk_dialog_run (GTK_DIALOG (dialog));
+  gtk_widget_destroy (GTK_WIDGET (dialog));
 
   g_free (comments);
   g_strfreev (artists);
@@ -2403,4 +2404,4 @@ window_cmd_toggle_reader_mode (GSimpleAction *action,
   active = ephy_web_view_get_reader_mode_state (web_view);
 
   ephy_web_view_toggle_reader_mode (web_view, !active);
-}
\ No newline at end of file
+}