Structure Block Preview Does Not Render Blocks Inside Sulfur Cube

Description: When using a Structure Block to save an area containing a Sulfur Cube that has consumed blocks, the blocks stored inside the Sulfur Cube are not rendered in the Structure Block's preview window.

Steps to Reproduce:

1. Place a Structure Block.

2. Within the Structure Block's defined area, generate or place several Sulfur Cubes that have consumed other blocks

3. Open the Structure Block's GUI to view the structure preview.

Observed Result: The preview area shows the Sulfur Cubes, but does not visually display the blocks they have consumed. The interior of the Sulfur Cube appears empty in the preview.

Expected Result: The Structure Block's preview should correctly render the blocks currently stored inside the Sulfur Cubes within its save area.