[gnome-software] snap: Fix compile warning

[Robert Ancell <rancell src gnome org>]

commit d528ca6e2805dbfb8b132a005afdc39c7673c56d
Author: Robert Ancell <robert ancell canonical com>
Date:   Tue Feb 12 16:09:35 2019 +1300

    snap: Fix compile warning

 plugins/snap/gs-plugin-snap.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)
---
diff --git a/plugins/snap/gs-plugin-snap.c b/plugins/snap/gs-plugin-snap.c
index 38da2b68..00d2e38b 100644
--- a/plugins/snap/gs-plugin-snap.c
+++ b/plugins/snap/gs-plugin-snap.c
@@ -160,7 +160,7 @@ load_auth (GsPlugin *plugin)
        g_autofree gchar *macaroon = NULL;
        g_autofree gchar *discharges_str = NULL;
        g_autoptr(GVariant) discharges_var = NULL;
-       g_autofree const gchar **discharges = NULL;
+       g_auto(GStrv) discharges = NULL;
        g_autoptr(SnapdAuthData) auth_data = NULL;
        g_autoptr(GError) error = NULL;
 
@@ -199,7 +199,7 @@ load_auth (GsPlugin *plugin)
                                                  discharges_str,
                                                  NULL, NULL, NULL);
        if (discharges_var)
-               discharges = g_variant_get_strv (discharges_var, NULL);
+               discharges = g_variant_dup_strv (discharges_var, NULL);
 
        priv->auth_data = snapd_auth_data_new (macaroon, discharges);
 }