Command in Command Block Minecart disappears from UI but still executes

When using a Command Block Minecart, if you enter a command and then close the UI, everything appears normal. However, when reopening the same command block minecart to view or edit the command, the command field is empty—as if no command was ever written.

Strangely, the previously entered command still executes when the minecart is powered/activated. This creates confusion, as the UI doesn't reflect the actual command stored in the block.

Steps to Reproduce

1. Place a command block minecart.

2. Open it and enter a command, e.g., /say Test.

3. Close the UI.

4. Reopen the command block minecart — the command field appears empty.

5. Power the minecart — the command executes regardless.

✅ Expected Behavior

The entered command should remain visible in the UI and editable when reopening the minecart.

❌ Actual Behavior

The UI shows no command, yet the command still executes when triggered.