Tag renaming can lead to duplicate tags in a document

This is a minor issue, not even sure if it is a bug

Steps to reproduce:

• on a page, add a tag, let's say space
• add another tag, let's say space1
• click on the space1 tag
• click on rename, and fill the field with space

You will have 2 identical tags. I check should be made when renaming the tag to see if the desired new tag name already exists or not.