[gnome-software] trivial: Don't show (null) in debugging output

[Richard Hughes <rhughes src gnome org>]

commit b45da72bd7ffa5e9aac0ddf6e55077c21cf2f027
Author: Richard Hughes <richard hughsie com>
Date:   Fri May 12 10:59:23 2017 +0100

    trivial: Don't show (null) in debugging output

 lib/gs-app.c |    9 ++++++---
 1 files changed, 6 insertions(+), 3 deletions(-)
---
diff --git a/lib/gs-app.c b/lib/gs-app.c
index e4b938a..4ae0705 100644
--- a/lib/gs-app.c
+++ b/lib/gs-app.c
@@ -402,13 +402,16 @@ gs_app_to_string (GsApp *app)
                          gs_app_get_kudos_percentage (app));
        if (app->name != NULL)
                gs_app_kv_lpad (str, "name", app->name);
-       gs_app_kv_printf (str, "pixbuf", "%p", app->pixbuf);
+       if (app->pixbuf != NULL)
+               gs_app_kv_printf (str, "pixbuf", "%p", app->pixbuf);
        for (i = 0; i < app->icons->len; i++) {
                AsIcon *icon = g_ptr_array_index (app->icons, i);
                gs_app_kv_lpad (str, "icon-kind",
                                as_icon_kind_to_string (as_icon_get_kind (icon)));
-               gs_app_kv_printf (str, "icon-pixbuf", "%p",
-                                 as_icon_get_pixbuf (icon));
+               if (as_icon_get_pixbuf (icon) != NULL) {
+                       gs_app_kv_printf (str, "icon-pixbuf", "%p",
+                                         as_icon_get_pixbuf (icon));
+               }
                if (as_icon_get_name (icon) != NULL)
                        gs_app_kv_lpad (str, "icon-name",
                                        as_icon_get_name (icon));