[gnome-boxes] Handle topology node missing from libvirt capabilities

[Christophe Fergeau <teuf src gnome org>]

commit 58d5ee3d21e4c307ff1e81f28ba033e4d3bd75a8
Author: Christophe Fergeau <cfergeau redhat com>
Date:   Tue Oct 2 17:46:27 2012 +0200

    Handle topology node missing from libvirt capabilities
    
    The <topology> node is not always present in libvirt capabilities
    XML (happened to me when running virsh capabilities in a F18 VM
    running on a F18 host). Boxes does not handle this situation, and
    tries to use the NULL capabilities pointer, which causes it to
    try to create a box with 0 vcpus, which is rejected by libvirt.
    
    This patch checks for NULL capabilities pointers, and falls back to
    not setting vcpu count nor topology when this happens as both attributes
    are optional. With this change, I can successfully create a box when Boxes
    is running in a VM.
    
    https://bugzilla.gnome.org/show_bug.cgi?id=685377

 src/vm-configurator.vala |    3 +++
 1 files changed, 3 insertions(+), 0 deletions(-)
---
diff --git a/src/vm-configurator.vala b/src/vm-configurator.vala
index de8b356..b7d74d0 100644
--- a/src/vm-configurator.vala
+++ b/src/vm-configurator.vala
@@ -164,6 +164,9 @@ private class Boxes.VMConfigurator {
     private static void set_cpu_config (Domain domain, Capabilities caps) {
         var topology = caps.get_host ().get_cpu ().get_topology ();
 
+        if (topology == null)
+            return;
+
         domain.vcpu = topology.get_sockets () * topology.get_cores () * topology.get_threads ();
 
         var cpu = new DomainCpu ();