fix for no extract results from uri check

lib/vagrant/downloaders/http.rb

@@ -8,7 +8,8 @@ module Vagrant
 
       def self.match?(uri)
         # URI.parse barfs on '<drive letter>:\\files \on\ windows'
-        URI.extract(uri).first.include?(uri)
+        uri = URI.extract(uri).first
+        uri && uri.include?(uri)
       end
         
       def download!(source_url, destination_file)

test/vagrant/downloaders/http_test.rb

@@ -39,6 +39,11 @@ class HttpDownloaderTest < Test::Unit::TestCase
       URI.expects(:extract).returns(['foo'])
       assert Vagrant::Downloaders::HTTP.match?('foo')
     end
+
+    should "return false if there are no extract results" do
+      URI.expects(:extract).returns([])
+      assert !Vagrant::Downloaders::HTTP.match?('foo')
+    end    
   end
 
   context "reporting progress" do