Guard against potential result_pdu nil in Net::LDAP::Connection#search

[jch]

It's possible for result_pdu to be nil at

ruby-net-ldap/lib/net/ldap/connection.rb

Line 548 in fd2d1ed

if result_pdu.result_code == Net::LDAP::ResultCodeSuccess and controls

. It's initially assigned on line 501, but only line 518 reassigns it. It's possible to get a nil if no SearchResult pdu's are seen. We should either raise an error or guard for the nil. Whoever picks this up should determine when this scenario can occur and include a failing test.

[zjuanma]

My application has this error in production environment, any solution?

[jch]

@zjuanma I haven't had time to work on this, but if you start a pull request, I'd be happy to review it.