[gnome-software] details page: Fix a compiler warning

[Kalev Lember <klember src gnome org>]

commit 397ca8a9881c2c5b7a711406d7b4b4e3073afd9f
Author: Kalev Lember <klember redhat com>
Date:   Wed Sep 26 15:30:56 2018 +0200

    details page: Fix a compiler warning
    
    I disagree with the compiler here, but let's just make it happy so that
    the warning noise doesn't drown real issues.

 src/gs-details-page.c | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)
---
diff --git a/src/gs-details-page.c b/src/gs-details-page.c
index 82f70b6f..68cde5a9 100644
--- a/src/gs-details-page.c
+++ b/src/gs-details-page.c
@@ -2044,12 +2044,18 @@ gs_details_page_app_removed (GsPage *page, GsApp *app)
        gs_details_page_reload (page);
 }
 
+static void
+show_all_cb (GtkWidget *widget, gpointer user_data)
+{
+       gtk_widget_show (widget);
+}
+
 static void
 gs_details_page_more_reviews_button_cb (GtkWidget *widget, GsDetailsPage *self)
 {
        self->show_all_reviews = TRUE;
        gtk_container_foreach (GTK_CONTAINER (self->list_box_reviews),
-                              (GtkCallback) gtk_widget_show, NULL);
+                              show_all_cb, NULL);
        gtk_widget_set_visible (self->button_more_reviews, FALSE);
 }