[gnome-software] trivial: Fix a tiny compiler warning

[Richard Hughes <rhughes src gnome org>]

commit 6cf5a5dbc9acc52e5f71503c734224777189a891
Author: Richard Hughes <richard hughsie com>
Date:   Fri Jun 10 16:15:09 2016 +0100

    trivial: Fix a tiny compiler warning

 src/gs-plugin.c |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)
---
diff --git a/src/gs-plugin.c b/src/gs-plugin.c
index 321c624..86a162b 100644
--- a/src/gs-plugin.c
+++ b/src/gs-plugin.c
@@ -928,7 +928,7 @@ gs_plugin_download_file (GsPlugin *plugin,
                             GS_PLUGIN_ERROR_FAILED,
                             "failed to download %s: %s",
                             uri, str->str);
-               return NULL;
+               return FALSE;
        }
        if (!g_file_set_contents (filename,
                                  msg->response_body->data,