Usually you don't have blank and question is opposite "how to how blank".
Could you check you don't have reference line on date, and could you attach packaged workbook for further analysis.
Find my approach as reference below and stored in attached workbook version 9.3
I first defined a calculation-field Date to get the full "Date-functionality" available in Tableau.
a. Date: date("01-"+mid([Transaction Date Month],6,2)+"-"+mid([Transaction Date Month],1,4))
b. Defined a Parameter: Week from today 1;52
b. show??:datediff('week',[Date],today())<=[Week from today] and datediff('week',[Date],today())>=0
Timeseries.twbx 19.0 KB