[gnome-boxes] express: Add a missing 'yield' keyword

[Zeeshan Ali Khattak <zeeshanak src gnome org>]

commit 8db661e4650b300e4d5ae89231079be69c36c981
Author: Zeeshan Ali (Khattak) <zeeshanak gnome org>
Date:   Fri Jan 13 22:19:39 2012 +0200

    express: Add a missing 'yield' keyword
    
    This was most probably the cause of recent regression in express
    installation cause without this keyword, we continue with the rest of the
    installation before the file gets copied, causing a race-condition.

 src/unattended-installer.vala |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)
---
diff --git a/src/unattended-installer.vala b/src/unattended-installer.vala
index 323552d..26732d3 100644
--- a/src/unattended-installer.vala
+++ b/src/unattended-installer.vala
@@ -281,7 +281,7 @@ private abstract class Boxes.UnattendedInstaller: InstallerMedia {
         var unattended_tmp_path = get_user_unattended_dir (unattended_dest_name);
         var unattended_tmp = File.new_for_path (unattended_tmp_path);
 
-        create_unattended_file (unattended_src, unattended_tmp, cancellable);
+        yield create_unattended_file (unattended_src, unattended_tmp, cancellable);
 
         debug ("Copying unattended file '%s' into disk drive/image '%s'", unattended_dest_name, disk_path);
         // FIXME: Perhaps we should use libarchive for this?