Undefined index: recaptcha_challenge_field in recaptcha.module on line 203.

Undefined index: recaptcha_challenge_field in recaptcha.module on line 203.
Undefined index: recaptcha_response_field in recaptcha.module on line 204.

I couldn't reproduce the error myself, but I see such errors regularly in my logs. I think those are created by register-spam-bots who are not configured to include the said fields!

We could at least repress the error message, and, maybe, add an entry in the logs about recaptcha having defeated another spambot! :)