I am tapping into the filter 'console_command_send_campaigns_before_send_to_subscriber' to call an external API. In some cases I want to remove the current email from the send process based on the API response. What is the appropriate return value if I dont want the current emailParams to be turned into an email and sent? If I return false from my addFilter function it seems to retry sending on the next processing cron instead of just skipping the recipient. Should I just return a null object?