[gthumb] jpeg: added note on why surface is set to NULL

[Paolo Bacchilega <paobac src gnome org>]

commit 2f1252dbf59c31a07cf7821ed51deb6fe394bcec
Author: Paolo Bacchilega <paobac src gnome org>
Date:   Thu Sep 20 11:47:57 2018 +0200

    jpeg: added note on why surface is set to NULL

 extensions/cairo_io/cairo-image-surface-jpeg.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
---
diff --git a/extensions/cairo_io/cairo-image-surface-jpeg.c b/extensions/cairo_io/cairo-image-surface-jpeg.c
index bc700c14..92abc051 100644
--- a/extensions/cairo_io/cairo-image-surface-jpeg.c
+++ b/extensions/cairo_io/cairo-image-surface-jpeg.c
@@ -582,7 +582,7 @@ _cairo_image_surface_create_from_jpeg (GInputStream  *istream,
                        g_set_error_literal (error, G_IO_ERROR, G_IO_ERROR_CANCELLED, "");
 
                cairo_surface_destroy (surface);
-               surface = NULL;
+               surface = NULL; /* ignore other jpeg errors */
        }
 
        if (read_all_scanlines)