[gthumb] image viewer: reset the builder to null after destroying it

[Paolo Bacchilega <paobac src gnome org>]

commit 869658875c9acca9d30a2640122d86fc6aa909ed
Author: Paolo Bacchilega <paobac src gnome org>
Date:   Fri Feb 14 08:55:55 2020 +0100

    image viewer: reset the builder to null after destroying it

 extensions/image_viewer/gth-image-viewer-page.c | 1 +
 1 file changed, 1 insertion(+)
---
diff --git a/extensions/image_viewer/gth-image-viewer-page.c b/extensions/image_viewer/gth-image-viewer-page.c
index d8785be1..9dcb1a54 100644
--- a/extensions/image_viewer/gth-image-viewer-page.c
+++ b/extensions/image_viewer/gth-image-viewer-page.c
@@ -1285,6 +1285,7 @@ gth_image_viewer_page_real_deactivate (GthViewerPage *base)
        }
 
        _g_object_unref (self->priv->builder);
+       self->priv->builder = NULL;
        _g_object_unref (self->priv->preloader);
        self->priv->preloader = NULL;
        self->priv->active = FALSE;