Fix T85157: join node not working when the second mesh is empty

The issue was that the `offset` in `dst_span[offset]` was out of bounds
when the domain size is 0. The fix is to simply skip copying attributes
in that case.

source/blender/nodes/geometry/nodes/node_geo_join_geometry.cc

@@ -163,6 +163,9 @@ static void fill_new_attribute(Span<const GeometryComponent *> src_components,
   int offset = 0;
   for (const GeometryComponent *component : src_components) {
     const int domain_size = component->attribute_domain_size(domain);
+    if (domain_size == 0) {
+      continue;
+    }
     ReadAttributePtr read_attribute = component->attribute_get_for_read(
         attribute_name, domain, data_type, nullptr);