Fix Cycles crash in Windows debug mode with volumes

intern/cycles/render/attribute.cpp

@@ -48,7 +48,7 @@ Attribute::Attribute(
 Attribute::~Attribute()
 {
   /* For voxel data, we need to free the image handle. */
-  if (element == ATTR_ELEMENT_VOXEL) {
+  if (element == ATTR_ELEMENT_VOXEL && buffer.size()) {
     ImageHandle &handle = data_voxel();
     handle.~ImageHandle();
   }

intern/cycles/render/attribute.h

@@ -59,7 +59,11 @@ class Attribute {
             AttributeElement element,
             Geometry *geom,
             AttributePrimitive prim);
+  Attribute(Attribute &&other) = default;
+  Attribute(const Attribute &other) = delete;
+  Attribute &operator=(const Attribute &other) = delete;
   ~Attribute();
+
   void set(ustring name, TypeDesc type, AttributeElement element);
   void resize(Geometry *geom, AttributePrimitive prim, bool reserve_only);
   void resize(size_t num_elements);

intern/cycles/render/image.cpp

@@ -119,6 +119,9 @@ void ImageHandle::clear()
   foreach (const int slot, tile_slots) {
     manager->remove_image_user(slot);
   }
+
+  tile_slots.clear();
+  manager = NULL;
 }
 
 bool ImageHandle::empty()