Make env[:subdomain] a string to allow for matching with empty regular

expressions.

Signed-off-by: Michael Bleigh <michael@intridea.com>

lib/subdomain_fu/routing_extensions.rb

@@ -10,7 +10,7 @@ def self.included(base)
 
     def recognition_conditions_with_subdomain
       result = recognition_conditions_without_subdomain
-      result << "conditions[:subdomain] === env[:subdomain]" if conditions[:subdomain] && conditions[:subdomain] != true && conditions[:subdomain] != false
+      result << "conditions[:subdomain] === env[:subdomain].to_s" if conditions[:subdomain] && conditions[:subdomain] != true && conditions[:subdomain] != false
       result << "SubdomainFu.has_subdomain?(env[:subdomain])" if conditions[:subdomain] == true
       result << "!SubdomainFu.has_subdomain?(env[:subdomain])" if conditions[:subdomain] == false
       result