Thank you for the development and maintenance of this extension.
Since robotMode is not set in ext_conf_template.txt and if it is set to 0 in Typoscript setup the call to ArrayUtility::mergeRecursiveWithOverrule in CaptchaService.php with includeEmptyValue set to false results in a configuration where robotMode is not defined.
Depending on the setup this may lead to unnecessary PHP warnings "Undefined array key".
Adding robotMode = 0 to ext_conf_template.txt would fix it.
Thank you for the development and maintenance of this extension.
Since robotMode is not set in ext_conf_template.txt and if it is set to 0 in Typoscript setup the call to ArrayUtility::mergeRecursiveWithOverrule in CaptchaService.php with includeEmptyValue set to false results in a configuration where robotMode is not defined.
Depending on the setup this may lead to unnecessary PHP warnings "Undefined array key".
Adding robotMode = 0 to ext_conf_template.txt would fix it.