YOY when we have data of selected month in current year then compare with same month in last year else entire year

I want to hide “NULL” values from the filter – but KEEP it always ON. Meaning i want it to actually NOT REMOVE what i’ve hidden

 

https://community.tableau.com/s/feed/0D5cw00000GgHmYCAV

Select Year/Quarter/Month then show Month like Jan -14, Feb-14 in dropdown and in order