Not sure if a bug or a feature request (probably one of each).
When a card is hidden due to no data, it would be nice to have the option to reflow all the cards below to fill the space. We have a data quality dashboard and it's quite common to have most of the questions empty. Hiding them seemed like a great idea except it leaves gaps making it more likely that the user won't scroll down to the bottom of the dashboard.
Edited as black background is a separate issue.