Current equivalent to old stop_if_no_target option?

Hello,

sbackup used to have an option called stop_if_no_target which, if set to 1, would only perform a backup if target path existed. This option was very useful in my setup because I use a USB drive as a backup target. This option made sbackup perfect for my needs. Now I see it was deprecated.

Is any other option or another way to accomplish the same task?

Thank you in advance,

Josep