[gtksourceview] StyleSchemeChooserWidget: fix compil warning (-Wcast-function-type)

[Sébastien Wilmet <swilmet src gnome org>]

commit 22a007f24c066018e2c96de066b1a2a41d93179f
Author: Sébastien Wilmet <swilmet gnome org>
Date:   Thu May 10 21:07:54 2018 +0200

    StyleSchemeChooserWidget: fix compil warning (-Wcast-function-type)

 gtksourceview/gtksourcestyleschemechooserwidget.c |    9 ++++++++-
 1 files changed, 8 insertions(+), 1 deletions(-)
---
diff --git a/gtksourceview/gtksourcestyleschemechooserwidget.c 
b/gtksourceview/gtksourcestyleschemechooserwidget.c
index 6c66627..f3e13c6 100644
--- a/gtksourceview/gtksourcestyleschemechooserwidget.c
+++ b/gtksourceview/gtksourcestyleschemechooserwidget.c
@@ -202,6 +202,13 @@ on_row_selected (GtkListBox                        *list_box,
 }
 
 static void
+destroy_child_cb (GtkWidget *widget,
+                 gpointer   data)
+{
+       gtk_widget_destroy (widget);
+}
+
+static void
 gtk_source_style_scheme_chooser_widget_populate (GtkSourceStyleSchemeChooserWidget *widget)
 {
        GtkSourceStyleSchemeChooserWidgetPrivate *priv = GET_PRIV (widget);
@@ -215,7 +222,7 @@ gtk_source_style_scheme_chooser_widget_populate (GtkSourceStyleSchemeChooserWidg
        g_signal_handlers_block_by_func (priv->list_box, on_row_selected, widget);
 
        gtk_container_foreach (GTK_CONTAINER (priv->list_box),
-                              (GtkCallback)gtk_widget_destroy,
+                              destroy_child_cb,
                               NULL);
 
        manager = gtk_source_style_scheme_manager_get_default ();