Long Text and Summary field (with unlimited value) adding extra textarea when editing the node

What are the steps required to reproduce the bug?

1. Create a content type and add a Long Text and Summary field.
2. Select 'Unlimited' in 'Number of Values' option of Long Text and Summary field
3. Create a node and add string to Long text and summary field and then save it.
4. Now edit that node. You will see Two Textarea, one with string you added and other one is empty

What behavior were you expecting?
When someone edit the node, he should see only one textarea in which he added the string. Not the blank one.

What happened instead?
Now when a user editing the node, there is two textarea, one in which he added the string and other one is blank.