Message field is not empty in preview mode for some bb codes

Some bb codes leave behind "traces" instead of an empty field after you click "Preview". Here are these codes: List, Add list item, Quote and Add syntax.

Steps to reproduce:
1) Open and login Jcommune in any browser.
2) Go to any topic and click “Answer” button.
3) Do not add any text in the Message field and click any BB-Code button (except IMG and URL BB-Codes buttons!)
4) Click “Preview” button.

Actual result: after clicking some bb codes (List, Add list item, Quote and Add syntax)the message field is not empty.
Expected result: after clicking any bb code (except IMG and URL BB-Codes buttons!)the message field must be empty.

Note: This bug was found in TC JC558 (#28).