Link without attributes are updated with previous autocomplete selection

Problem/motivation

There's an issue where when you are updating links without data attributes, they get updated with last autocomplete selection.

Steps to reproduce

1. Create content with 2 links without data attributes.
2. Click on first link and "Edit link".
3. Use autocomplete and select item from it.
4. Click on "Save".
5. Click on second link and "Edit link".
6. Click on "Save".
7. Click on "Source" to display source.
8. Second link should not have data attributes, but it has data attributes filled in with first link values.

Proposed resolution