Fix T95532: Merge node deletes everything for empty selections

The problem was that nullptr was returned which is a valid value for
Mesh * and hence the returned optional was treated as having some value.
There was no check for point clouds so that was fixed as well.

Differential Revision: https://developer.blender.org/D14026

1 files changed, 4 insertions, 2 deletions

diff --git a/source/blender/nodes/geometry/nodes/node_geo_merge_by_distance.cc b/source/blender/nodes/geometry/nodes/node_geo_merge_by_distance.cc
index 3c790079b5b..89227c773cc 100644
--- a/source/blender/nodes/geometry/nodes/node_geo_merge_by_distance.cc
+++ b/source/blender/nodes/geometry/nodes/node_geo_merge_by_distance.cc
@@ -60,7 +60,7 @@ static std::optional<Mesh *> mesh_merge_by_distance(const MeshComponent &mesh_co
 
   const IndexMask selection = evaluator.get_evaluated_as_mask(0);
   if (selection.is_empty()) {
-    return nullptr;
+    return std::nullopt;
   }
 
   const Mesh &mesh = *mesh_component.get_for_read();
@@ -78,7 +78,9 @@ static void node_geo_exec(GeoNodeExecParams params)
     if (geometry_set.has_pointcloud()) {
       PointCloud *result = pointcloud_merge_by_distance(
           *geometry_set.get_component_for_read<PointCloudComponent>(), merge_distance, selection);
-      geometry_set.replace_pointcloud(result);
+      if (result) {
+        geometry_set.replace_pointcloud(result);
+      }
     }
     if (geometry_set.has_mesh()) {
       std::optional<Mesh *> result = mesh_merge_by_distance(