Merge pull request #383 from railsstarter/topic/fix_for_undefined_met…

…hod_write_for_nilclass

fix for undefined method for write exception

lib/net/ldap/connection.rb

@@ -690,7 +690,7 @@ def delete(args)
   #
   # Typically a TCPSocket, but can be a OpenSSL::SSL::SSLSocket
   def socket
-    return @conn if defined? @conn
+    return @conn if defined?(@conn) && !@conn.nil?
 
     # First refactoring uses the existing methods open_connection and
     # prepare_socket to set @conn. Next cleanup would centralize connection