[gtk/wip/baedert/for-master] inspector: Avoid some failing casts

[Timm Bäder <baedert src gnome org>]

commit 911503e7ef088137eccdbaf09c04d59b6b0157c4
Author: Timm Bäder <mail baedert org>
Date:   Sat Aug 1 08:56:34 2020 +0200

    inspector: Avoid some failing casts
    
    We might be inspecting a non-widget here, so can't just cast that.

 gtk/inspector/window.c | 12 +++++++++---
 1 file changed, 9 insertions(+), 3 deletions(-)
---
diff --git a/gtk/inspector/window.c b/gtk/inspector/window.c
index 7d7ec56f4b..61b3a9aed9 100644
--- a/gtk/inspector/window.c
+++ b/gtk/inspector/window.c
@@ -919,9 +919,15 @@ update_go_buttons (GtkInspectorWindow *iw)
   switch (kind)
     {
     case CHILD_KIND_WIDGET:
-      update_go_button (iw->go_down_button, gtk_widget_get_first_child (GTK_WIDGET (object)) != NULL, "First 
child");
-      update_go_button (iw->go_previous_button, gtk_widget_get_prev_sibling (GTK_WIDGET (object)) != NULL, 
"Previous sibling");
-      update_go_button (iw->go_next_button, gtk_widget_get_next_sibling (GTK_WIDGET (object)) != NULL, "Next 
sibling");
+      update_go_button (iw->go_down_button,
+                        GTK_IS_WIDGET (object) &&gtk_widget_get_first_child (GTK_WIDGET (object)) != NULL,
+                        "First child");
+      update_go_button (iw->go_previous_button,
+                        GTK_IS_WIDGET (object) && gtk_widget_get_prev_sibling (GTK_WIDGET (object)) != NULL,
+                        "Previous sibling");
+      update_go_button (iw->go_next_button,
+                        GTK_IS_WIDGET (object) && gtk_widget_get_next_sibling (GTK_WIDGET (object)) != NULL,
+                        "Next sibling");
       gtk_widget_hide (iw->list_position_label);
       break;
     case CHILD_KIND_LISTITEM: