Simple Payments Block: Settings Lost When Switching Between Code Editor and Visual Editor

#### Steps to reproduce the issue

1. Add a Simple Payment block to a post or page.
2. Enter all of the information into the block.
3. Switch to the Code Editor.
4. Switch back to Visual Editor.

#### What I expected
All of the Simple Payment block settings should be retained.

#### What happened instead
The Simple Payment block is empty.

**Screenshots/Video**
Link to a video showing this issue:

https://d.pr/v/ACcf3i

Discovered while working with user here: 2400948-zen

Reproduce the reported sequence with a Simple Payment block, entering settings before switching from the Code Editor to the Visual Editor. Compare the block state before and after the switch and trace the editor transition to identify where the settings are lost. Done means all entered settings remain intact after returning to the Visual Editor.

Written by the indexing model from the issue text.