[gnome-builder] flatpak: check for env before accessing it

[Christian Hergert <chergert src gnome org>]

commit 2eb81a374c6c911ba656f974b425d9edf9c29514
Author: Christian Hergert <chergert redhat com>
Date:   Wed Jul 4 23:48:54 2018 +0200

    flatpak: check for env before accessing it

 src/plugins/flatpak/gbp-flatpak-manifest.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)
---
diff --git a/src/plugins/flatpak/gbp-flatpak-manifest.c b/src/plugins/flatpak/gbp-flatpak-manifest.c
index b5e51e772..99813a3c3 100644
--- a/src/plugins/flatpak/gbp-flatpak-manifest.c
+++ b/src/plugins/flatpak/gbp-flatpak-manifest.c
@@ -222,7 +222,8 @@ discover_environ (GbpFlatpakManifest *self,
 
   env = ide_configuration_get_environment (IDE_CONFIGURATION (self));
 
-  if ((obj = json_object_get_object_member (build_options, "env")))
+  if (json_object_has_member (build_options, "env") &&
+      (obj = json_object_get_object_member (build_options, "env")))
     {
       JsonObjectIter iter;
       const gchar *key;