Fix bypass bug with malformed addresses

The Ruby Resolv library can return an empty array from getaddresses for
some atypical IP address encodings. This was brought to my attention by
@EdOverflow.

lib/private_address_check.rb

@@ -31,6 +31,8 @@ def private_address?(address)
 
   def resolves_to_private_address?(hostname)
     ips = Resolv.getaddresses(hostname)
+    return true if ips.empty?
+
     ips.any? do |ip| 
       private_address?(ip)
     end

test/private_address_check_test.rb

@@ -35,4 +35,8 @@ def test_private_hostname_for_public_addresses
   def test_private_hostname_for_private_addresses
     assert PrivateAddressCheck.resolves_to_private_address?("localhost")
   end
+
+  def test_private_address_for_malformed_addresses
+    assert PrivateAddressCheck.resolves_to_private_address?("127.1")
+  end
 end