After blocks are unselected, it's necessary to trigger an Action so that keystroke action handlers will be updated in Application._handle_action. In my previous pull request, I achieved this by replacing a FlowGraph.update_selected() call with a FlowGraph.update_selected_elements() call, since the latter happens to trigger an Action. However, this does not occur in all cases, because FlowGraph.update_selected_elements() can return early. To fix the issue, I've reverted that change and changed the DrawingArea's focus-out-event handler to explicitly trigger Actions.ELEMENT_SELECT(). After this change, blocks appear to be unselect in all cases when accessing the block search box.