[gnome-boxes/gnome-3-34] media-manager: Don't enumerate unexisting installer medias

[Felipe Borges <felipeborges src gnome org>]

commit 0c4027290d45ee7d57ae4483af30b7dc9242a2a6
Author: Felipe Borges <felipeborges gnome org>
Date:   Tue Aug 27 15:06:01 2019 +0300

    media-manager: Don't enumerate unexisting installer medias
    
    Fixes #399

 src/media-manager.vala | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)
---
diff --git a/src/media-manager.vala b/src/media-manager.vala
index b8977deb..adf8c97e 100644
--- a/src/media-manager.vala
+++ b/src/media-manager.vala
@@ -114,7 +114,9 @@ else if (VMConfigurator.is_libvirt_cloning_config (config))
 
                 var media = yield create_installer_media_for_path (path);
 
-                list.append (media);
+               if (media != null) {
+                    list.append (media);
+               }
             } catch (GLib.Error error) {
                 warning ("Failed to get information on device '%s': %s. Ignoring..", path, error.message);
             }