safe navigation operator on res

modules/exploits/unix/webapp/wp_wpdiscuz_unauthenticated_file_upload.rb

@@ -69,7 +69,7 @@ class MetasploitModule < Msf::Exploit::Remote
 
   def find_wmusecurity_id
     res = send_request_cgi({ 'uri' => normalize_uri(target_uri.path, blogpath) })
-    wmusecurity_id = res.body.match(/wmuSecurity":"(\w+)/)&.captures
+    wmusecurity_id = res&.body.match(/wmuSecurity":"(\w+)/)&.captures
     unless wmusecurity_id
       fail_with(Failure::NotFound, 'Failed to retrieve the wmusecurity id')
     end