In Dashboard (not Classic), when I set up layer actions of Layer #1 to enable filtering of a list widget of Layer #2, the pop-up of Layer #1 becomes completely unusable when there are zero results in the list widget of Layer #2. The pop-up text disappears and the Select tools do nothing. The pop-up and select tools work great if there is at least one result.
For example, I have a Cases point layer and Inspections point layer. When I click on a case and there have not been any inspections, the pop-up becomes unusable until you unselect the feature.
However, if there has been at least one inspection for the case, the pop-up continues to work great.