Fix blank values for LDAP NTLM auth

Author: zeroSteiner

lib/metasploit/framework/ldap/client.rb

@@ -82,8 +82,8 @@ def ldap_auth_opts_kerberos(opts)
         def ldap_auth_opts_ntlm(opts)
           auth_opts = {}
           ntlm_client = RubySMB::NTLM::Client.new(
-            opts[:username],
-            opts[:password],
+            (opts[:username].nil? ? '' : opts[:username]),
+            (opts[:password].nil? ? '' : opts[:password]),
             workstation: 'WORKSTATION',
             domain: opts[:domain].blank? ? '.' : opts[:domain],
             flags: