Index: core/mui/gtk_extension.rb
===================================================================
--- core/mui/gtk_extension.rb	(revision 609)
+++ core/mui/gtk_extension.rb	(working copy)
@@ -201,6 +201,7 @@
     def url_open_command
       openable_commands = %w{xdg-open open /etc/alternatives/x-www-browser}
       wellknown_browsers = %w{firefox chrome opera}
+      command = nil
       catch(:urlopen) do
         openable_commands.each{ |o|
           if command_exist?(o)