Check res properly and update Ruby syntax

If res is nil, it should not be doing res.code

Author: wchen-r7

modules/exploits/unix/webapp/sugarcrm_rest_unserialize_exec.rb

@@ -65,7 +65,12 @@ def exploit
         }
     })
 
-    if not res or res.code != 200
+    unless res
+      print_error('Connection timed out while sending a request to rest.php')
+      return
+    end
+
+    if res && res.code != 200
       print_error("#{peer} - Exploit failed: #{res.code}")
       return
     end
@@ -81,7 +86,7 @@ def exploit
       'headers' => { 'payload' => Rex::Text.encode_base64(payload.encoded) }
     })
 
-    if res and res.code != 200
+    if res && res.code != 200
       print_error("#{peer} - Payload execution failed: #{res.code}")
       return
     end