[gnome-software/gnome-3-22] trivial: Fix make check with a clean checkout

[Richard Hughes <rhughes src gnome org>]

commit 5d26ecf13ff70f445bdfa14932b901468f856ec7
Author: Richard Hughes <richard hughsie com>
Date:   Mon Sep 19 10:35:42 2016 +0100

    trivial: Fix make check with a clean checkout

 src/gs-self-test.c |    3 ++-
 1 files changed, 2 insertions(+), 1 deletions(-)
---
diff --git a/src/gs-self-test.c b/src/gs-self-test.c
index 4223739..364b69c 100644
--- a/src/gs-self-test.c
+++ b/src/gs-self-test.c
@@ -907,7 +907,8 @@ gs_plugin_loader_flatpak_func (GsPluginLoader *plugin_loader)
 
        /* no files to use */
        repodir_fn = gs_test_get_filename ("tests/flatpak/repo");
-       if (!g_file_test (repodir_fn, G_FILE_TEST_EXISTS)) {
+       if (repodir_fn == NULL ||
+           !g_file_test (repodir_fn, G_FILE_TEST_EXISTS)) {
                g_test_skip ("no flatpak test repo");
                return;
        }