Gutenberg: Undo pastes the copied text

[GutenDev]

Describe the bug
I copied a text and pasted it on a paragraph block, hit Return and clicked command+z; the text pasted twice;

To Reproduce
Steps to reproduce the behavior:

1. Copy a text
2. Paste it on a paragraph block
3. Hit Return
4. Hit Command+Z / Ctrl+Z

Expected behavior
Should delete the new paragraph block created.

Screenshots

Desktop (please complete the following information):

• OS: macOS
• Browser Google Chrome
• Version 70.0.3538.77

[swissspidy]

Noticed the same behavior a short while ago in https://github.com/WordPress/gutenberg/issues/6516#issuecomment-433920438.

[afercia]

Seems to me it happens also witn an already existing paragraph. Just make sure to:

• put the caret _at the beginning_ of the paragraph
• press Enter
• a new paragraph is created _before_ the existing one (I guess Gutenberg considers the previous one as "deleted"?)
• press Command+Z / Ctrl+Z: the previous paragraph re-appears

[designsimply]

Closing as a duplicate of #8882. @GutenDev I think a fix for #8882 will cover this case as well, but please let me know if you feel otherwise!