[goffice] GODoc: avoid critical.

[Morten Welinder <mortenw src gnome org>]

commit 2f98e3f7d64cfeed71d67e11ac6f689c8ac79bc2
Author: Morten Welinder <terra gnome org>
Date:   Thu Jun 11 17:04:01 2020 -0400

    GODoc: avoid critical.

 NEWS                 | 3 +++
 goffice/app/go-doc.c | 2 +-
 2 files changed, 4 insertions(+), 1 deletion(-)
---
diff --git a/NEWS b/NEWS
index 6c38206c..5ec83e17 100644
--- a/NEWS
+++ b/NEWS
@@ -7,6 +7,9 @@ Jean:
        * Optimize GtkWidget embedding in the canvas. See #465.
        * Clip grid lines rendering to the plot area. [#50]
 
+Morten:
+       * Avoid critical in document image handling.
+
 --------------------------------------------------------------------------
 goffice 0.10.47:
 
diff --git a/goffice/app/go-doc.c b/goffice/app/go-doc.c
index 08456fee..6e7c8ffc 100644
--- a/goffice/app/go-doc.c
+++ b/goffice/app/go-doc.c
@@ -595,7 +595,7 @@ go_doc_save_image (GODoc *doc, char const *id)
        if (!doc)
                return;
        if (!g_hash_table_lookup (doc->priv->imagebuf, id)) {
-               GOImage *image = g_hash_table_lookup (doc->images, id);
+               GOImage *image = go_doc_get_image (doc, id);
                if (image)
                        g_hash_table_replace (doc->priv->imagebuf,
                                              g_strdup (id),