Skip labelling if no src path present

Fixes startup of guest's with sourceless cdrom devices.

Patch from Cole Robinson originally posted here:

  https://bugzilla.redhat.com/499569

but never sent upstream.
Signed-off-by: NMark McLoughlin <markmc@redhat.com>

ChangeLog

+Thu Jul  3 11:27:14 GMT 2009 Mark McLoughlin <markmc@redhat.com>
+
+	Patch from Cole Robinson in https://bugzilla.redhat.com/499569
+
+	* src/security_selinux.c: Skip labelling if no src path
+	present
+
 Thu Jul  3 11:26:04 GMT 2009 Mark McLoughlin <markmc@redhat.com>
 
 	Patch from Tim Waugh in https://bugzilla.redhat.com/507555

src/security_selinux.c

@@ -380,6 +380,9 @@ SELinuxSetSecurityImageLabel(virConnectPtr conn,
 {
     const virSecurityLabelDefPtr secdef = &vm->def->seclabel;
 
+    if (!disk->src)
+        return 0;
+
     if (disk->shared) {
         return SELinuxSetFilecon(conn, disk->src, default_image_context);
     } else if (disk->readonly) {