Lighting issues in the dark spaces below farmland.

Short description of the issue

Build a dark, enclosed space using grass blocks, oak wood, and quartz blocks, or more blocks, cover the top with farmland, and address the lighting issue inside the space. Just like Figures 1, 2, 3, and 4.

Steps to reproduce the issue

Using the blocks mentioned above, build a hollow cube, and change the top to be covered with farmland, the minimum size is 3*3.

Then go inside and observe. Just like Figures 2, 3, and 4.

Expected result

The entire space is completely dark.

Actual result

The blocks around the top edges emit a faint glow. Just like Figures 2, 3, and 4.