[gnome-boxes] installer-media: Allow adding empty cdrom device

[Zeeshan Ali Khattak <zeeshanak src gnome org>]

commit 54cb121c2d59b344f1ab47e70be40141b74cdbb7
Author: Zeeshan Ali (Khattak) <zeeshanak gnome org>
Date:   Mon Jun 1 13:52:36 2015 +0100

    installer-media: Allow adding empty cdrom device
    
    i-e a CD-ROM drive without any disk in it.
    
    https://bugzilla.gnome.org/show_bug.cgi?id=748962

 src/installer-media.vala |    5 +++--
 1 files changed, 3 insertions(+), 2 deletions(-)
---
diff --git a/src/installer-media.vala b/src/installer-media.vala
index 5963222..2eba022 100644
--- a/src/installer-media.vala
+++ b/src/installer-media.vala
@@ -129,7 +129,7 @@ private class Boxes.InstallerMedia : GLib.Object {
 
     protected void add_cd_config (Domain         domain,
                                   DomainDiskType type,
-                                  string         iso_path,
+                                  string?        iso_path,
                                   string         device_name,
                                   bool           mandatory = false) {
         var disk = new DomainDisk ();
@@ -139,7 +139,8 @@ private class Boxes.InstallerMedia : GLib.Object {
         disk.set_driver_name ("qemu");
         disk.set_driver_format (DomainDiskFormat.RAW);
         disk.set_target_dev (device_name);
-        disk.set_source (iso_path);
+        if (iso_path != null)
+            disk.set_source (iso_path);
         disk.set_target_bus (DomainDiskBus.IDE);
         if (mandatory)
             disk.set_startup_policy (DomainDiskStartupPolicy.MANDATORY);