Check if DN exists

https://bugs.ruby-lang.org/issues/16830

Author: nobu

lib/uri/ldap.rb

@@ -118,6 +118,7 @@ def initialize(*arg)
 
     # Private method to cleanup +dn+ from using the +path+ component attribute.
     def parse_dn
+      raise InvalidURIError, 'bad LDAP URL' unless @path
       @dn = @path[1..-1]
     end
     private :parse_dn

test/uri/test_ldap.rb

@@ -95,6 +95,10 @@ def test_select
       u.select(:scheme, :host, :not_exist, :port)
     end
   end
+
+  def test_parse_invalid_uri
+    assert_raise(URI::InvalidURIError) {URI.parse("ldap:https://example.com")}
+  end
 end