How do i get a rollup with formula Min()to stop returning zero when rolling up empty cells?

In [Workers] I have a rollup field called {Lowest_rating} which uses the Min() formula to return the lowest number a worker has in [Worker Interactions]. FWIW, the field in [Worker Interactions] that is being rolled-up is a number field.

Where the worker has no rating yet, the rollup returns a “0”. I find this to be visually confusing. Is there anyway in the rollup to return the cell empty rather than a zero? Photos below.

thanks!