Steps to reproduce

1. Log in to back office.
2. Go to Content / Content types / Content.
3. Start creating a new CT.
4. Add field type 'matrix' to created CT.
5. In field type matrix add new column at the bottom of form.
6. Fill in inputs 'Name' and 'Identifier'. 
7. Clear inputs by clicking on 'X' button inside the input.

Actual result:

Clearing input doesn't work using "x" button.

Expected result:

Clearing input data using "x" button works properly.

Note:
On edit field type form clearing input data works good.