[gtk/wip/chergert/for-master] textview: fix precondition assertions

[Christian Hergert <chergert src gnome org>]

commit 1e994419ee172906b0d9edd7a3fe7490f9c2aba6
Author: Christian Hergert <chergert redhat com>
Date:   Tue Nov 24 08:29:52 2020 -0800

    textview: fix precondition assertions
    
    It is a programmer error to call this with a child widget that has not
    been placed within the GtkTextView.
    
    Fixes #3386

 gtk/gtktextview.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)
---
diff --git a/gtk/gtktextview.c b/gtk/gtktextview.c
index 59a4c41a8a..f038b300ac 100644
--- a/gtk/gtktextview.c
+++ b/gtk/gtktextview.c
@@ -9289,11 +9289,11 @@ gtk_text_view_move_overlay (GtkTextView *text_view,
 {
   g_return_if_fail (GTK_IS_TEXT_VIEW (text_view));
   g_return_if_fail (GTK_IS_WIDGET (child));
-  g_return_if_fail (gtk_widget_get_parent (child) == GTK_WIDGET (text_view));
+  g_return_if_fail (text_view->priv->center_child != NULL);
+  g_return_if_fail (gtk_widget_get_parent (child) == (GtkWidget *)text_view->priv->center_child);
 
-  if (text_view->priv->center_child == NULL)
-    gtk_text_view_child_move_overlay (text_view->priv->center_child,
-                                      child, xpos, ypos);
+  gtk_text_view_child_move_overlay (text_view->priv->center_child,
+                                    child, xpos, ypos);
 }