[gtk] magnifier: Don't try to use a null widget paintable

[Timm Bäder <baedert src gnome org>]

commit 600952e295f3ab09fb9e8a68b8932114c4c28c9c
Author: Timm Bäder <mail baedert org>
Date:   Sun Mar 22 15:41:40 2020 +0100

    magnifier: Don't try to use a null widget paintable
    
    We destroy the paintable in dispose, which can be called multiple times.

 gtk/gtkmagnifier.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)
---
diff --git a/gtk/gtkmagnifier.c b/gtk/gtkmagnifier.c
index 143e98827d..049ea2e082 100644
--- a/gtk/gtkmagnifier.c
+++ b/gtk/gtkmagnifier.c
@@ -158,7 +158,9 @@ gtk_magnifier_dispose (GObject *object)
   GtkMagnifier *self = GTK_MAGNIFIER (object);
   GtkMagnifierPrivate *priv = gtk_magnifier_get_instance_private (self);
 
-  _gtk_magnifier_set_inspected (self, NULL);
+  if (priv->paintable)
+    _gtk_magnifier_set_inspected (self, NULL);
+
   g_clear_object (&priv->paintable);
 
   G_OBJECT_CLASS (gtk_magnifier_parent_class)->dispose (object);