rem: gtk_widget_set_sensitive ( g_object_get_data ( assistant, "button_next" ), FALSE );
add: gtk_widget_set_sensitive ( g_object_get_data ( G_OBJECT (assistant), "button_next" ), FALSE );
context: void import_preview_maybe_sensitive_next ( GtkWidget * assistant, GtkTreeModel * model ) {    GtkTreeIter iter;    /* Don't allow going to next page if no file is selected yet. */    gtk_widget_set_sensitive ( g_object_get_data ( assistant, "button_next" ), FALSE );    gtk_tree_model_get_iter_first ( model, &iter );    if ( ! gtk_tree_store_iter_is_valid ( model, &iter ))    {	return;    }    /* Iterate over lines so we check if some are checked. */    do     {	gboolean selected;	enum import_type type;	gtk_tree_model_get ( GTK_TREE_STORE ( model ), &iter, 			     IMPORT_FILESEL_SELECTED, &selected, 			     IMPORT_FILESEL_TYPE, &type,			     -1 );	if ( selected && type != TYPE_UNKNOWN )	{	    gtk_widget_set_sensitive ( g_object_get_data ( assistant, "button_next" ), 				       TRUE );	    return;	}    }    while ( gtk_tree_model_iter_next ( model, &iter ) );}