[gnome-software/gnome-3-22] trivial: Fix a console warning when refining flatpak apps

[Richard Hughes <rhughes src gnome org>]

commit a3636353ce0f243b02359a4adfbc5453539570cc
Author: Richard Hughes <richard hughsie com>
Date:   Tue Sep 20 14:35:42 2016 +0100

    trivial: Fix a console warning when refining flatpak apps

 src/plugins/gs-appstream.c |    5 ++++-
 1 files changed, 4 insertions(+), 1 deletions(-)
---
diff --git a/src/plugins/gs-appstream.c b/src/plugins/gs-appstream.c
index ff8fb02..03e8658 100644
--- a/src/plugins/gs-appstream.c
+++ b/src/plugins/gs-appstream.c
@@ -530,7 +530,10 @@ gs_appstream_refine_app (GsPlugin *plugin,
                gs_app_set_id (app, as_app_get_id (item));
 
        /* set source */
-       gs_app_set_metadata (app, "appstream::source-file", as_app_get_source_file (item));
+       if (gs_app_get_metadata_item (app, "appstream::source-file") == NULL) {
+               gs_app_set_metadata (app, "appstream::source-file",
+                                    as_app_get_source_file (item));
+       }
 
        /* scope */
        if (gs_app_get_scope (app) == AS_APP_SCOPE_UNKNOWN &&