account for changed itineraries once landmarks are marked as done or deleted

frontend/lib/modules/current_trip_landmarks_list.dart

@@ -1,3 +1,5 @@
+import 'dart:developer';
+
 import 'package:flutter/material.dart';
 
 import 'package:anyway/structs/landmark.dart';
@@ -24,10 +26,16 @@ List<Widget> landmarksList(Trip trip, {required bool Function(Landmark) selector
         LandmarkCard(landmark, trip),
       );
 
-      if (!landmark.visited && landmark.next != null) {
-        children.add(
-          StepBetweenLandmarks(current: landmark, next: landmark.next!)
-        );
+      if (!landmark.visited) {
+        Landmark? nextLandmark = landmark.next;
+        while (nextLandmark != null && nextLandmark.visited) {
+          nextLandmark = nextLandmark.next;
+        } 
+        if (nextLandmark != null) {
+          children.add(
+            StepBetweenLandmarks(current: landmark, next: nextLandmark!)
+          );
+        }
       }
     }
   }