Fix crashing if slicing with non organic tree support (#14074)

Fix non organic tree support crashing

Fix Orca crashing during slicing if non organic tree support is used

src/libslic3r/ShortestPath.cpp

@@ -6,6 +6,7 @@
 
 #include "clipper.hpp"
 #include "ShortestPath.hpp"
+#include "ExtrusionEntityCollection.hpp"
 #include "KDTreeIndirect.hpp"
 #include "MutablePriorityQueue.hpp"
 #include "Print.hpp"
@@ -15,6 +16,30 @@
 
 namespace Slic3r {
 
+// Orca: Some support entities may contain empty nested paths, which cannot be reordered safely.
+static bool extrusion_entity_has_endpoints(const ExtrusionEntity *entity)
+{
+    auto paths_have_endpoints = [](const ExtrusionPaths &paths) {
+        return !paths.empty() &&
+               !paths.front().polyline.points.empty() &&
+               !paths.back().polyline.points.empty();
+    };
+
+    if (entity == nullptr)
+        return false;
+    if (const auto *collection = dynamic_cast<const ExtrusionEntityCollection *>(entity))
+        return !collection->entities.empty() &&
+               extrusion_entity_has_endpoints(collection->entities.front()) &&
+               extrusion_entity_has_endpoints(collection->entities.back());
+    if (const auto *path = dynamic_cast<const ExtrusionPath *>(entity))
+        return !path->polyline.points.empty();
+    if (const auto *multipath = dynamic_cast<const ExtrusionMultiPath *>(entity))
+        return paths_have_endpoints(multipath->paths);
+    if (const auto *loop = dynamic_cast<const ExtrusionLoop *>(entity))
+        return paths_have_endpoints(loop->paths);
+    return true;
+}
+
 // Naive implementation of the Traveling Salesman Problem, it works by always taking the next closest neighbor.
 // This implementation will always produce valid result even if some segments cannot reverse.
 template<typename EndPointType, typename KDTreeType, typename CouldReverseFunc>
@@ -1035,8 +1060,10 @@ void chain_and_reorder_extrusion_entities(std::vector<ExtrusionEntity*> &entitie
 
 void chain_and_reorder_extrusion_entities(std::vector<ExtrusionEntity*> &entities, const Point *start_near)
 {
-    // this function crashes if there are empty elements in entities
+    // Orca: Reordering queries first_point() / last_point(); drop entities that cannot provide valid endpoints.
-    entities.erase(std::remove_if(entities.begin(), entities.end(), [](ExtrusionEntity *entity) { return static_cast<ExtrusionEntityCollection *>(entity)->empty(); }),
+    entities.erase(std::remove_if(entities.begin(), entities.end(), [](ExtrusionEntity *entity) {
+        return !extrusion_entity_has_endpoints(entity);
+    }),
                    entities.end());
 	reorder_extrusion_entities(entities, chain_extrusion_entities(entities, start_near));
 }

src/libslic3r/Support/TreeSupport.cpp

@@ -1332,7 +1332,12 @@ static void make_perimeter_and_infill(ExtrusionEntitiesPtr& dst, const ExPolygon
             dst = std::move(loops_entities);
         }
     }
-    dst.erase(std::remove_if(dst.begin(), dst.end(), [](ExtrusionEntity *entity) { return static_cast<ExtrusionEntityCollection *>(entity)->empty(); }), dst.end());
+
+    // Orca: Some entities are direct paths, so check the type before testing for an empty collection.
+    dst.erase(std::remove_if(dst.begin(), dst.end(), [](ExtrusionEntity *entity) {
+        return entity != nullptr && entity->is_collection() && static_cast<ExtrusionEntityCollection *>(entity)->empty();
+    }), dst.end());
+
     if (infill_first) {
         // sort regions to reduce travel
         Points ordering_points;