Trix adds newline after list

If there is a list (ordered or unordered) at the end of the data, trix adds another `

` to the end. So if you submit the data and reopen the editor three times you have 3 extra lines in the data.

##### Steps to Reproduce

1. Click in the editor and insert a list with text
2. Submit the data and reopen it
3. Now you have an extra newline at the end
4. Repeat 2. for more extra lines

##### Details

* Trix version: 2.0.5
* Browser name and version: Chrome latest 3 versions
* Operating system: Windows, Linux

Reproduce the issue in Trix 2.0.5 using Chrome and the listed ordered or unordered list steps. Trace what happens when the submitted data is reopened, and verify that repeated reopen cycles no longer append an extra

or newline.

Written by the indexing model from the issue text.