[gnome-software] trivial: Fix up some broken error handling in the flatpak plugin

[Richard Hughes <rhughes src gnome org>]

commit 9e11355f9d7f7633b8cda460dc500989ff01c8a6
Author: Richard Hughes <richard hughsie com>
Date:   Wed Feb 22 10:46:34 2017 +0000

    trivial: Fix up some broken error handling in the flatpak plugin

 src/plugins/gs-flatpak.c |    2 ++
 1 files changed, 2 insertions(+), 0 deletions(-)
---
diff --git a/src/plugins/gs-flatpak.c b/src/plugins/gs-flatpak.c
index 7a75e88..cdaa3ca 100644
--- a/src/plugins/gs-flatpak.c
+++ b/src/plugins/gs-flatpak.c
@@ -1792,6 +1792,8 @@ gs_plugin_refine_item_metadata (GsFlatpak *self,
        } else {
                data = gs_flatpak_fetch_remote_metadata (self, app, cancellable,
                                                         error);
+               if (data == NULL)
+                       return FALSE;
                str = g_bytes_get_data (data, &len);
        }