Fix that resolves the issue when trying to add a new key-value pair.

[borjajimnz]

Description

Fix that resolves the issue when trying to add a new key-value pair described in #15416.
This was my fault in the last fix. now is solved. soz!

Visual changes

https://www.youtube.com/watch?v=WP4hgMzWZ4A

Functional changes

• Code style has been fixed by running the composer cs command.
• Changes have been tested to not break existing functionality.
• Documentation is up-to-date.

[rickzim]

Hey! i used the updated code in the demo project but now theres another weird issue (maybe its just me but it doesn't hurt to test it)

if you add new rows to a KeyValue field, and populate it, it will start doing weird things like removing other rows.

It is the easiest to trigger if you add multiple empty lines at ones, and then try to populate them.

[danharrin]

Adding rows definitely needs to update the state otherwise it will be out of sync

[danharrin]

I am going to revert the old PR and make a new release

[danharrin]

Going to close this, but please reopen when the above issue is addressed