Fix T102700: Viewer node missing check for empty geometry component

`GeometrySet::has()` can return an empty component. It's more convenient
if it doesn't, since other code rarely wants to access an empty component.

The alternative would be adding an `is_empty()` check in the lazy function
for the viewer node, that would work fine too, for this case.

Differential Revision: https://developer.blender.org/D16584

source/blender/blenkernel/intern/geometry_set.cc

@@ -161,7 +161,8 @@ const GeometryComponent *GeometrySet::get_component_for_read(
 
 bool GeometrySet::has(const GeometryComponentType component_type) const
 {
-  return components_[component_type].has_value();
+  const GeometryComponentPtr &component = components_[component_type];
+  return component.has_value() && !component->is_empty();
 }
 
 void GeometrySet::remove(const GeometryComponentType component_type)

source/blender/modifiers/intern/MOD_nodes.cc

@@ -1016,9 +1016,6 @@ static Vector<OutputAttributeToStore> compute_attributes_to_store(
       continue;
     }
     const GeometryComponent &component = *geometry.get_component_for_read(component_type);
-    if (component.is_empty()) {
-      continue;
-    }
     const blender::bke::AttributeAccessor attributes = *component.attributes();
     for (const auto item : outputs_by_domain.items()) {
       const eAttrDomain domain = item.key;

source/blender/nodes/geometry/nodes/node_geo_sample_index.cc

@@ -111,9 +111,6 @@ static bool component_is_available(const GeometrySet &geometry,
     return false;
   }
   const GeometryComponent &component = *geometry.get_component_for_read(type);
-  if (component.is_empty()) {
-    return false;
-  }
   return component.attribute_domain_size(domain) != 0;
 }
 

source/blender/nodes/geometry/nodes/node_geo_sample_nearest.cc

@@ -211,9 +211,6 @@ static bool component_is_available(const GeometrySet &geometry,
     return false;
   }
   const GeometryComponent &component = *geometry.get_component_for_read(type);
-  if (component.is_empty()) {
-    return false;
-  }
   return component.attribute_domain_size(domain) != 0;
 }