Private messages: Incorrect layout when subject is very long

Pre-conditions:
There are User_1 and User_2

Steps to reproduce:
1. Login to Forum as User_1 and go to 'Messages'
2. Create a private message with a very long subject
(eg:wwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwww)
3. Click 'Save' button and overview 'Drafts' folder layout
4. Reopen the message, enter User_2 in 'To' field and some text in 'Message content'
5. Click 'Send' button and overview 'Outbox' folder layout
6. Login as User_2 and go to 'Messages'
7. Overview 'Inbox' folder layout

Actual result:
There is no word-wrap so 'Subject' column is too wide when PM subject is very long
Expected result:
There is word-wrap so all columns' width is as usual when PM subject is very long