[gnome-builder] flatpak: only access length field of existing array

[Georges Basile Stavracas Neto <gbsneto src gnome org>]

commit ff29eab7ba1211dab1348aad44ec63ad50504e7e
Author: Georges Basile Stavracas Neto <georges stavracas gmail com>
Date:   Tue Feb 14 17:27:42 2017 -0200

    flatpak: only access length field of existing array
    
    It causes a segmentation fault when it fails to detect
    the runtimes.

 plugins/flatpak/gbp-flatpak-preferences-addin.c |    3 +++
 1 files changed, 3 insertions(+), 0 deletions(-)
---
diff --git a/plugins/flatpak/gbp-flatpak-preferences-addin.c b/plugins/flatpak/gbp-flatpak-preferences-addin.c
index 0881a25..b950c52 100644
--- a/plugins/flatpak/gbp-flatpak-preferences-addin.c
+++ b/plugins/flatpak/gbp-flatpak-preferences-addin.c
@@ -109,6 +109,9 @@ add_runtimes (GbpFlatpakPreferencesAddin *self,
                                                              NULL,
                                                              NULL);
 
+          if (refs == NULL)
+            return;
+
           for (guint j = 0; j < refs->len; j++)
             {
               FlatpakRemoteRef *ref = g_ptr_array_index (refs, j);