Land rapid7#15047, Correct DNS PTR record crash

Author: smcintyre-r7

lib/msf/core/exploit/remote/dns/enumeration.rb

@@ -189,8 +189,8 @@ def dns_get_ptr(ip)
     records = []
     resp.answer.each do |r|
       next unless r.class == Dnsruby::RR::IN::PTR
-      records << r.ptr.to_s
-      print_good("#{ip}: PTR: #{r.ptr} ")
+      records << r.rdata.to_s
+      print_good("#{ip}: PTR: #{r.rdata} ")
     end
     return if records.blank?
     dns_note(ip, 'DNS PTR records', records) if datastore['DnsNote']