* Linear Navigation: Fix showing arrows when last slide has vertical children

js/reveal.js

@@ -3951,6 +3951,11 @@
 			}
 		}
 
+		if( config.navigationMode === "linear" ) {
+			routes.right = routes.right || routes.down;
+			routes.left = routes.left || routes.up;
+		}
+
 		// Reverse horizontal controls for rtl
 		if( config.rtl ) {
 			var left = routes.left;