[gnome-boxes] Fix a check in commit 91fe7f3

[Zeeshan Ali Khattak <zeeshanak src gnome org>]

commit 744859effeba1c1b32c58a836e860f2eb85cf7ff
Author: Zeeshan Ali (Khattak) <zeeshanak gnome org>
Date:   Fri Jun 8 17:14:44 2012 +0300

    Fix a check in commit 91fe7f3
    
    Check for short ID of the OS being longer than 15 characters, not label.

 src/win7-installer.vala |    6 ++++--
 1 files changed, 4 insertions(+), 2 deletions(-)
---
diff --git a/src/win7-installer.vala b/src/win7-installer.vala
index 9276d11..dfbcebc 100644
--- a/src/win7-installer.vala
+++ b/src/win7-installer.vala
@@ -41,7 +41,9 @@ private class Boxes.Win7Installer: WindowsInstaller {
         // Remove '.' and everything after it
         lang = /\..*/i.replace (lang, -1, 0, "");
 
-        if (label.length > 15)
-            critical ("'%s' is longer than 15 characters, expect %s express installation to fail!", label, os.name);
+        if (os != null && os.short_id.length > 15)
+            critical ("'%s' is longer than 15 characters, expect %s express installation to fail!",
+                      os.short_id,
+                      os.name);
     }
 }