input/seatop_default: release on empty workspace

Instead of handling presses and releases on empty workspaces as setting
focus to the workspace, handle releases by notifying the seat of a
pointer action. This way DnDs are correctly released if the button is
released over an empty workspace.

Fixes swaywm#3932

sway/input/seatop_default.c

@@ -279,8 +279,12 @@ static void handle_button(struct sway_seat *seat, uint32_t time_msec,
 	}
 
 	// Handle clicking an empty workspace
-	if (node && node->type == N_WORKSPACE) {
-		seat_set_focus(seat, node);
+	if (node && node->type == N_WORKSPACE ) {
+		if ( state == WLR_BUTTON_PRESSED) {
+			seat_set_focus(seat, node);
+		} else {
+			seat_pointer_notify_button(seat, time_msec, button, state);
+		}
 		return;
 	}