Filter for multiple parameters which may be blank or have a value

Trying get Filters to work for parameters that may or may not have values.

query brings back all the data i need.  so i want to FILTER based on parameters.

i have defined param1 and param2 each as multi-value, allow blanks.

i have set the filter at each group level (from top down to detail), but i dont get results.

expected results:  if param1 has a value and param2 does not, i should see all data based on param1

                          if param2 has a value and param1 does nto, i should see all data based on param2

looking for all combinations of parameters having values(even multiples) or no values at all.