[BUG] Previous comment is saved upon the creation a new one

**Describe the bug**
When we create a new comment it saves the previous comment, which forces the user to delete the
content before writing a new one.

**To Reproduce**
Steps to reproduce the behavior:
1. Go to any widget parameter menu (three vertical buttons at the top right widget window)
2. Click on 'Comment' then on the 'New Comment' green button at the bottom and write a new comment.
3. Click on a 'New comment' again after saving your previous comment.
4. You should notice that your previous comment is saved but still present on the interface.

**Expected behavior**
We expect the comment to be empty so the user does not have to delete his previous comment to write a new one.

**Screenshots**

**Desktop (please complete the following information):**
- Browser [e.g. chrome, safari]

**Additional context**
Add any other context about the problem here.