[gnome-builder] glade: fix over-zealous assertion

[Christian Hergert <chergert src gnome org>]

commit e7bef0d1cc608d031d9c8b28a3e2b83315245b5a
Author: Christian Hergert <chergert redhat com>
Date:   Wed Oct 24 13:49:44 2018 -0700

    glade: fix over-zealous assertion
    
    This can be non-widgets too, like a GtkSizeGroup.

 src/plugins/glade/gbp-glade-layout-stack-addin.c | 2 --
 1 file changed, 2 deletions(-)
---
diff --git a/src/plugins/glade/gbp-glade-layout-stack-addin.c 
b/src/plugins/glade/gbp-glade-layout-stack-addin.c
index d2967a89e..8246960f2 100644
--- a/src/plugins/glade/gbp-glade-layout-stack-addin.c
+++ b/src/plugins/glade/gbp-glade-layout-stack-addin.c
@@ -70,8 +70,6 @@ gbp_glade_layout_stack_addin_selection_changed_cb (GbpGladeLayoutStackAddin *sel
       const gchar *name;
       const gchar *icon_name;
 
-      g_assert (GTK_IS_WIDGET (widget));
-
       name = glade_widget_get_name (glade);
       display_name = glade_widget_get_display_name (glade);
       icon_name = glade_widget_adaptor_get_icon_name (adapter);