I would basically use the same approach as described here:
Meaning you simply insert the new record into your target table, but before doing so you explicitly check whether the LKP on the GENDER column returned some value; if not, forward a NULL to your target, otherwise forward the return value of the LKP.
Does that make sense? Maybe I've worded this too complicated, hence my question.
Thank you, i tested via using Expression transformation, it works perfectly.